Fix incompatibility with python 2.7.6.
[Geolib] Fix object redefinition.
Update sympy to version 0.7.5
Fix latex issues with sympy O.7.5
Fix remaining issue with new sympy version (sip error when running tests).
Don't allow multiple roots in module `Exercices tableaux de signes`.
Module sip must be imported before sympy.
[FS#279] In module tablatex, tabvar() handles abs() now.
Improve dependancies detection at geophar launch.

Config files are also located in ~/.config/geophar by now.