Added `string` to list of ignored scopes in several files

Hi,
In the course of developing an answer for [this question](http://stackoverflow.com/questions/26049019/disable-code-completion-inside-quotes-in-sublime-text-3) on Stack Overflow, I discovered that several of the `.sublime-completion` files were creating their active scopes by starting with `source.php`, then subtracting what wasn't wanted. Unfortunately, `string` wasn't one of the subtracted scopes, so completions were being suggested when just typing strings. I modified the files in question to add `- string` to their scopes, and also bumped the version number in the `VERSION` file in anticipation of a new release if this pull request is accepted.

Please let me know if you need anything else, or have any questions or anything.

Matt