implement spell checking targets to aid tech writers and documentation contributors

- add two new targets to our Makefile: `spell' and `spell_all'
- we rely on `aspell' spell checking tool (http://aspell.net/), it must
  be installed in system
- `spell' target triggers aspell to check files that were touched by
  current commit; suggested workflow:
  * git checkout -b release-notes-vX.Y
  * edit files with your favourite editor
  * git commit -a
  * make spell
  * git commit --amend
  * git review
- `spell_all' target will run aspell against all .rst files found in
  pages/ directory
- provide aspell wordlist `.aspell_en.wordlist', so that aspell would
  not ask you each time when it finds unknown word or acronym (e.g.
  VLAN, PXE, DHCP, etc)
- mention `aspell' in README.md

Change-Id: I87a3dcdf5e3e926f737933a00c7597065e4f80ee

.aspell_en.wordlist

@@ -0,0 +1,224 @@
+personal_ws-1.1 en 223
+AMQP
+API
+APIs
+Arista
+assignee
+AWS
+backend
+backends
+backplane
+balancer
+balancers
+behaviour
+binded
+bootable
+bootloader
+Brasero
+Broadcom
+CCISS
+Ceilometer
+CentOS
+Ceph
+checkbox
+CIB
+CIDR
+Cirros
+Cisco
+CLI
+Cloudera
+CloudFormation
+ClusterLabs
+colocation
+ConnectX
+corosync
+Cygwin
+datacenter
+datastore
+Datastores
+DHCP
+DNS
+DoS
+dropdown
+DRS
+ESX
+ESXi
+eth
+Etherpad
+failover
+FCoE
+filesystem
+FlatDHCP
+FlatDHCPManager
+FlatManager
+frontend
+Galera
+Gerrit
+GHz
+GRE
+GRO
+GTID
+GUID
+Hadoop
+HAproxy
+HAProxy
+hardcoded
+Haswell
+HDD
+HDP
+HealthCheck
+Heartbleed
+HortonWorks
+hostname
+hypervisor
+hypervisors
+IaaS
+IceHouse
+IDE
+iDRAC
+IEEE
+IIS
+IMG
+ImgBurn
+InfraRecorder
+IOMMU
+IOPS
+IOV
+IP
+IPMI
+IPs
+iptables
+IRC
+iSCSI
+iSER
+JBOD
+jpg
+JSON
+JVM
+KVM
+LACP
+LBaaS
+LDAP
+Lenovo
+lifecycle
+login
+lookups
+loopback
+LVM
+LXC
+MBR
+Mellanox
+memcached
+metadata
+middleware
+Mirantis
+Mnesia
+MongoDB
+MTU
+multi
+multicast
+Murano
+MySQL
+Nagios
+Nailgun
+namespace
+namespaces
+Netgear
+NFS
+Nginx
+NIC
+NICs
+NSX
+NTP
+OEM
+online
+openssh
+OpenSSL
+openstack
+OpenStack
+OpenSUSE
+OSD
+OSI
+OSTF
+overcommit
+oversubscription
+OVS
+PageBreak
+paravirtualized
+Paxos
+PCnet
+pdf
+PKI
+plugin
+png
+PostgreSQL
+POSTROUTING
+PowerEdge
+prefetch
+PuppetDB
+PXE
+pxelinux
+QEMU
+RabbitMQ
+RADOS
+RadosGW
+RBD
+RESTful
+RHEL
+RPC
+rst
+rsyslogd
+runtime
+SATA
+Scalability
+Screenshots
+SLB
+SNAT
+SQL
+SQLAlchemy
+SSD
+startup
+Stateful
+stderr
+STP
+subnet
+subnets
+sudo
+symlinks
+Synchrony
+syslog
+TCP
+TFTP
+TODO
+UDP
+UEFI
+UI
+ULV
+untagged
+upgraders
+uplink
+USB
+UUID
+VBoxManage
+vboxnet
+vCenter
+VirtualBox
+virtualization
+virtualize
+virtualized
+VLAN
+VLANManager
+VLANs
+VM
+VMDK
+vMotion
+VMs
+VMware
+VMWare
+VNC
+vSphere
+vSwitch
+workflow
+XFS
+yaml
+Zabbix

Makefile

@@ -16,7 +16,9 @@ I18NSPHINXOPTS  = $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) .
 
 IMAGEDIRS     = _images
 
-.PHONY: help clean html dirhtml singlehtml pickle json htmlhelp qthelp devhelp epub latex latexpdf pdf text man changes linkcheck doctest gettext
+.PHONY: help clean html dirhtml singlehtml pickle json htmlhelp qthelp devhelp \
+	epub latex latexpdf pdf text man changes linkcheck doctest gettext spell \
+	spell_all
 
 help:
 	@echo "Please use \`make <target>' where <target> is one of"
@@ -40,10 +42,12 @@ help:
 	@echo "  changes    to make an overview of all changed/added/deprecated items"
 	@echo "  linkcheck  to check all external links for integrity"
 	@echo "  doctest    to run all doctests embedded in the documentation (if enabled)"
+	@echo "  spell      to run aspell against .rst files changed in current commit"
+	@echo "  spell_all  to run aspell against all .rst files in pages/ directory"
 
 clean:
 	-rm -rf $(BUILDDIR)/*
-	-@rm -f $(PDFs) 
+	-@rm -f $(PDFs)
 
 # Pattern rule for converting SVG to PDF
 %.pdf : %.svg
@@ -172,3 +176,20 @@ doctest:
 	$(SPHINXBUILD) -b doctest $(ALLSPHINXOPTS) $(BUILDDIR)/doctest
 	@echo "Testing of doctests in the sources finished, look at the " \
 	      "results in $(BUILDDIR)/doctest/output.txt."
+
+SPELL = aspell
+ASPELLOPTS = --dont-backup -d en --personal=.aspell_en.wordlist
+RSTS := $(shell find pages/ -type f -name '*.rst')
+
+COMMIT_RSTS := $(shell git diff-tree --no-commit-id --name-only -r HEAD)
+spell:
+	@for rst in $(COMMIT_RSTS); do \
+		$(SPELL) $(ASPELLOPTS) check $$rst; \
+	done
+
+spell_all:
+	@for rst in $(RSTS); do \
+		$(SPELL) $(ASPELLOPTS) check $$rst; \
+	done
+	@echo "Spell check complete"
+

README.md

@@ -31,11 +31,11 @@ To get started, you need to install all necesasary tools.
 
 On Debian/Ubuntu:
     
-    sudo apt-get install git python-pip python-dev make imagemagick libjpeg-dev inkscape
+    sudo apt-get install git python-pip python-dev make imagemagick libjpeg-dev inkscape aspell
 
 On Fedora:
 
-	sudo yum install git python-pip python-devel make ImageMagick libjpeg-turbo-devel inkscape
+	sudo yum install git python-pip python-devel make ImageMagick libjpeg-turbo-devel inkscape aspell
 
 Among other things that installs
 [ImageMagick](http://www.imagemagick.org/ "ImageMagick") and