Add possibility to run selected code from a temporary file instead of passing code in args

`context.getFileWithCode()` can be used in grammars instead of `context.getCode()` allowing to run selected code with languages that don't have interpreters like `php -r`. Tested with PHP on Win7 (see example in grammars.coffee with PHP language).

On Windows it's very useful because I had some problems with line breaks in terminal causing some parse errors...

Edit
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* Added dependency to node-uuid used in file path
That's what I was getting at (`hasPrefixSelected` would perform the search). Either way we'd have to check, plus it isn't a complex check to add in line.