add: show changes like current branch

You can also show current changes adding __git_ps1_changes to PS1 close to __git_ps1:
PS1='[\u@\h \W$(__git_ps1 " (%s)")$(__git_ps1_changes " (%s)")]\$ '

Example:
-----------

	[user@host (master) ^2 +3 *1 ?6]$ 
^2 +3 *1 ?6 means:
 * ^2  Your branch is ahead of 'origin/branch' by 2 commits
 * +3  Your branch has 3 staged changes to be commited
 * *1  Your branch has 1 unstaged changes to be commited
 * ?6  Your branch has 6 untracked files