Added branch-alias to version output when no tags present

Added branch-alias for dev-master to ```--version|-V``` output when current version is actually a revision (a non release/git tag).
Example:

Before:
```
$ composer --version
Composer version 73e9db5d9952d52a46ecbc20a269a8c5f9c5b011 2014-10-07 15:03:19
```

After:
```
$ composer --version
Composer version 1.0-dev (73e9db5d9952d52a46ecbc20a269a8c5f9c5b011) 2014-10-07 15:03:19
```

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Doc PR        | none