add git status source
add cr to last line
modify file status
add zaw-git-status into readme
support ZAW_EDITOR value

Usually many user use EDITOR as commit message editor, so
EDITOR block process.
Therefore I don't want to block process when editor is opened
from zaw. So I use separate environment value ZAW_EDITOR.
If ZAW_EDITOR value is not set, zaw try to use EDITOR.
support sub dir action
Merge pull request #27 from byplayer/git-add

support git status souce
Merge pull request #28 from byplayer/zaw-editor

support ZAW_EDITOR value
zaw-src-open-file: fix parameter expansion flag