Rather than have the python literal string, use CMake's find_package
to find actual python executable. This is more useful if you have
both Python 2 and 3 installed. CMake currently only supports python 2
and so will automatically find that version
* Removed useless include_directories
* Print ssl library path in build summary
* ExternalProject also exists on 2.8.0
* include pummel tests when testing with ctest
* Moved tests.cmake to test/CMakeList.txt
* Removed inconsistent, unnecessary condition in else
Squashed commit of ca128f7dcd28cbcfba154c8577ed54d4aa71dd02 with
contributions from Mark Constable (markc@renta.net) and Daniel Gröber
(darklord@darkboxed.org).
