GIT_PROMPT_END was broken on directories without repository

fixes #19
Updated Installation instructions
Fix for when spaces exists in repo path
Merge pull request #21 from bwestlin/master

Fix for when spaces exists in repo path
Fix indent and Strip traling spaces
Merge pull request #22 from tuxinaut/master

Fix indent and Strip traling spaces
Made the check for upstream changes asynchronous. Fixes #23