installation: Python-2.6 and pip requirements
- Increases minimal Python version requirement to v2.6. There will be soon lots of code merged to the master branch, coming from INSPIRE, that is no longer Python-2.4 compatible. The time has come to abandon Python-2.4 compatibility!
- Inclusion of pip requirements files suitable for the master branch.
Signed-off-by: Tibor Simko <tibor.simko@cern.ch>