Small improvements

Redeclare Blue colour used to display virtualenv name: the color didn't
work in git repositories.

Removed ResetColor local: has no effect as ResetColor is already global
and we don't change it here.
Don't color the brackets around virtualenv name
Fix for case when __GIT_PROMPT_DIR contains spaces
Merge pull request #43 from mar-pet/master

Small improvements
Added config variable to preserve old PS1 outside of git repositories. Fixes #44
Wrapped prompt colors in \[ and \] to fix history. Should fix #45
Fix typo

Closing '}' should come before '\]', not after
Merge pull request #47 from hdeheer/master

Fix typo
Revert "Fix typo"

This reverts commit 12c2305329753576126cfe6f341d91f75f4e251e.
Revert "Wrapped prompt colors in \[ and \] to fix history."
Fixes #48 for now

This reverts commit 6acf7f8d3ec689f1f38c19a54a73b46f13ad1db6.
Fixed git status is broken on branch name containing forward-slash.
Merge pull request #50 from garryyao/fix/git-status

Fixed git status is broken on branch name containing forward-slash.
Made gitstatus variables for `symbols_ahead`, `symbols_behind` and `symbols_prehash` configurable via `git-prompt-colors.sh`
Fixes #51

The new variables are:

```bash
GIT_STATUS_SYMBOLS_AHEAD
GIT_STATUS_SYMBOLS_BEHIND
GIT_STATUS_SYMBOLS_PREHASH
```