Improve detection speed for LSB based systems

The new code avoids calling the external lsb_release
binary and reads the /etc/lsb-release issue file instead.
Fix KeyError exception on non-LSB systems
Switch to platform module for LSB detection
Merge branch 'lsbfix' of https://github.com/fkie/rospkg
cleaning up tests for #28
fixing unit tests to run on precise
cleaning up pep8 compliance and comments from review
full pep8 check
Merge pull request #32 from ros/unittest_fixes

patches for unit test portability
1.0.19
adding raring
1.0.20 a new version is easier than clearing failed uploads
updating urls to be more generic