Update tox and requirements

requirements.txt

@@ -1,3 +1,4 @@
 charm-tools
 flake8
 ruamel.yaml==0.10.12
+simplejson

tox.ini

@@ -3,6 +3,7 @@ skipsdist = True
 envlist = pep8
 
 [testenv]
+basepython = python2.7
 setenv = VIRTUAL_ENV={envdir}
          PYTHONHASHSEED=0
          TERM=linux
@@ -15,14 +16,12 @@ install_command =
 deps =
   -r{toxinidir}/requirements.txt
 
-[testenv:generate]
-basepython = python2.7
+[testenv:build]
 commands =
-  charm generate --log-level DEBUG -o {toxinidir}/build src
+  charm-build --log-level DEBUG -o {toxinidir}/build src
 
 [testenv:venv]
 commands = {posargs}
 
 [testenv:pep8]
-basepython = python2.7
 commands = flake8 {posargs} src/reactive src/lib