SBP library path issue about mav_rtk_gps

[marco-tranzatto]

From Python Documentation:

When a module named spam is imported, the interpreter first searches for a built-in module with that name. If not found, it then searches for a file named spam.py in a list of directories given by the variable sys.path. sys.path is initialized from these locations: (1) the directory containing the input script (or the current directory), (2) PYTHONPATH (a list of directory names, with the same syntax as the shell variable PATH), (3) the installation-dependent default.

By printing sbp.client.__file__ (__file__ is the pathname of the file from which the module was loaded, if it was loaded from a file), I could double check that, despite of the PYTHONPATH set in .bashrc, the sbp modules are always loaded from /usr/local/lib/python2.7/dist-packages/sbp-2.2.1-py2.7.egg/sbp

[marco-tranzatto]

Addressed in PR #24.

Since it is unlikely for a system to use both PiksiV2 and Piksi Multi, the cleanest solution is to use the default path of Python, where SBP module gets installed, and do not modify PYTHONPATH in .bashrc.