Bugfix for #3356 (workaround)

```http://getcomposer.org/version``` is still returning commit reference (only git signature), and this
URI is used to compare the local version against latest:

Example:
```
$ curl http://getcomposer.org/version
c33c5196b19c77ea89b05a81c573d88543d3a93d
```
while ```Composer::VERSION``` now is ```1.0-dev (c33c5196b19c77ea89b05a81c573d88543d3a93d)```.

@Seldaek, how can I see the controller logic for ```/version``` endpoint in http://getcomposer.org? Maybe it's a minor change.
I hope your opinion. 

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #3356
| Doc PR        | none