Fix python3 compatability for version number

This fixes  #716 for python3 following the spirit of 8586c58a.

unittest/srdf: fix vector size

This was causing bugs in DEBUG mode

Fix issue when hpp-fcl is missing

Related to #729

[Model] Total mass

[parsers/urdf] Add inline to member function retrieveCollisionGeometry

doc: fix value in bounds check

math: remove unused PId variable

Fix doc issues related to new gepetto-viewer API modifications

[SRDF]  Fix parsing of reference config + Add ability to read a SRDF stream. 

[doc] [bindings] Small fixes to doxygen and Python bindings

Make assertion more robust

Add __version__ variable to Python

  In log_SO2 (-I2), theta might be set to -PI and atan2 might return PI.

Fix and examples