Release RBTools 0.5.6.
Add setup-repo documentation to the index.

The documentation for the setup-repo command was included in the tree
but was not specified in the index.txt, preventing it from appearing in
the list of commands. The documentation page was reachable by URL, but
not really discoverable.
Fix perforce posting from subdirectories of the client root.

The logic that checked whether we were inside a p4 client was adding
os.path.pathsep to the path name instead of os.path.sep. This meant that we'd
only match if the cwd was the client root.

Testing done:
* Made a subdirectory in a p4 client and posted a change.

Fixes bug 3218.

Reviewed at https://reviews.reviewboard.org/r/5390/