Precompilation and line endings in YTemplater

Added information about how YTemplater makes use of line endings when precompiling template files.

This will help people to understand how YTemplater works and hopefully get ride of issues like the one described in https://github.com/orionhealth/ytemplater/issues/6. 
The unit test failing was when running it under the Y.Handlebars engine. In Y.Handlebars, the templater.revive method is overridden by the function template, were the environment variable is used to call methods like:
* env.VM.checkRevision
* env.VM.invokePartial
* env.compile

All those methods are existing within the engine object itself, hence me passing it as parameter.