Adding tests for PythonModule
Python package lookup warns when installing outside python path

It is possible to install packages to locations outside the python path. The
python package lookup now warns when this happens.  It also honors the
LOCAL_PYTHON_EXECUTABLE variable which sets up a build-local python
environment.
Adding ability to compile cython extensions
Python extensions accept explicit target name
Add add_pytest function

Adds any numbers of python tests for the py.test framework.
These tests are not installed. That would be the job of the add_python_module
function.
:bug: when installing python extension

Bug appears when location variable is empty. It is empty when the extension is
not contained within a package.
add_python_module accepts configurable files

All *.in.* are passed through configure_file with @ONLY.
Add function so ctest can work with py.test
:lipstick: so things fit in 80 columns
Removed unused option from add_python_module
Install python packages via pip first
Revert "Install python packages via pip first"

This reverts commit 135712055836bf28d435f35371401bf602203018.
:bug: when EXTERNAL_ROOT is not an absolute path

CMake does not expand "~/" unless requested.
This lead to issues when installing python packages via easy_install.
Add more output when required python package fails to install
Setuptools sometimes (?) returns None
Test was installing cython to wrong path
Merge pull request #12 from UCL/python

Python