* Linux/Debian - ensure python-pip & python-dev are installed
* LinuxRHEL/CentOS - ensure python-virtualenv & python-devel are
installed
* Darwin/OSX - check & exit if pip not installed
* Always rebuild the venv
* Dropped the path on wget, to allow for platform path differences
* Dropped the -N on wget, as it has no effect when using -O and
github aren't returning the Last-Modified header
Change-Id: I221965ee1b1776d46f4b6fba00ffb7069e5b34f8
Simon McCartney