Versioning in tests

For the automated mentoring project, it is valuable to know what version of the test data things are being solved against. Tracks are tending to add a comment to the tests file to achieve this, which is a sensible solution in my opinion. However, the formats different signifcantly. For example:

Csharp:
```
// This file was auto-generated based on version 1.7.0 of the canonical data.
```

Ruby
```
# Common test data version: 1.0.0 e1c6d44
```

PHP
```
/**
* @exercism-version 1.4.0
*/
```

I think it would be nice to standardise on a string format that we use across tracks. Does anyone have any opinions or thoughts on this, or what we should choose?