Use Pickle as binary sources cache.

The cPickle serialization module is almost eight times
as fast as the generic YAML loader, and still almost
twice as fast as the optimized CLoader.

You have to run 'rosdep update' to rebuild the cache
in the binary format. If no binary cache files are
found, the code falls back to the old YAML
serialization.
fixing unit tests for cPickle conversion #222
simpler if statement
do not fall back to writing out yaml cache file, let the exception bubble up
do not silently fail if cache is invalid (aka cannot load pickle file)
0.10.14
Revert "Use CLoader for improved YAML parsing speed."

This reverts commit 89a6848cc8cc98e2e830b8b6072e73a68d78f9a9.
Merge remote-tracking branch 'origin/master'