Generate a channel specific version file.

This is the first step in updating the emberjs.com/builds site's various channel sections to know about which version it is mirroring. The idea is to be able to let people know what the last tagged version for a given channel was.

This PR will generate a file in each 'channel' directory with the following directory structure:

```
/release/<dasherized project name>-version.json
/beta/<dasherized project name>-version.json
/canary/<dasherized project name>-version.json
```

The contents of each file will be:

```json
{
    "projectName": "Ember Data",
    "projectFilter": "ember-data",
    "lastRelease": "1.1.0-beta.1",
    "futureVersion": "1.1.0",
    "channel": "beta",
    "date": "2013-09-13"
}
```
A companion PR will be submitted to the website shortly...