Fix bug with git bash prompt

With git 2.9.3 uses the word tree instead of directory. This would mean the
dirty git flag was always showing in the bash prompt. Now look for tree
and directory.

bash/functions

@@ -23,7 +23,8 @@ function parse_git_status {
     if [[ $(git status 2> /dev/null | wc -l) -eq 0 ]]; then
         return
     fi
-    if [[ $(git status 2> /dev/null | grep "working directory clean" | wc -l) -eq 0 ]]; then
+
+    if [[ $(git status 2> /dev/null | grep -E "working tree|directory clean" | wc -l) -eq 0 ]]; then
         echo ' ∓'
     fi
 }