Git-x

Fixed issues:

* it's not working on mac os with python 2.7
* `git b` command ouput the wrong branch.

Fix git cia -x command:
-x didn's work if the file already in the index.

Add --graph/-g, --author/-a, and --date/-d options to git llg command

`git llg -g` to show graph.

`git llg -gad` to show graph with author and date.


Thanks iliafrenkel for the command

git pr` supports to raise pull request to bitbucket.