Update shellista.py

various fixes and minor additions, including:
* replaced `.rstrip('/')` with `os.path.normpath()` to fix handling of paths like `/`
* simple OSError handler in `do_ls` to avoid crashing the shell when ls'ing a forbidden file
* documented/added help text for a couple commands and aliases
* minor code style things here and there
Merge pull request #1 from dgelessus/patch-1

Update shellista.py
Create Readme.md

To document the origin of Shellista
Update Readme.md
Merge pull request #2 from cclauss/patch-1

Create Readme.md
Update Readme.md
Merge pull request #3 from cclauss/patch-1

Update Readme.md
Update Readme.md

Add new additions info
Update Readme.md
Merge pull request #7 from cclauss/patch-2

Update Readme.md
Update Readme.md

Slight modification of opening sentence
Update Readme.md

Add title
Update Readme.md

Fix title sizes
Wrap onecmd with a try/catch for unhandled exceptions
Change downloaded version of Gittle
add basic git checkout for branches only
Prettify git log
Hack to get dulwich submodules working
tabcmplte
Merge pull request #12 from jsbain/master

tab completion