Add Documentation to Help Contributors

[ejmr]

@zonuexe

Based on some recent comments I've read in issues and pull-requests, how do you feel about adding a document specifically for programmers who want to contribute to PHP Mode? The document would describe things like:

• Any code standards you want people to follow.
• A descrption of a useful workflow, e.g.:
  ** Creating a branch with a useful name and types of names to avoid, like ejmr/bugfixes.
  ** Sanity checks to run before opening a pull-request, like running the test suite.
  ** On that topic: notes about using and (maybe more important in my opinion) expanding the test suite for all new features.
  ** How to seek peer-review for any non-trivial, non-tiny submissions.
• Practices to follow for writing documentation.
• And practices for writing good Git commit messages, with stuff like:
  ** Referencing previous commits when appropriate, especially for bug fixes.
  ** Including useful metadata in commit messages such as links to relevant GitHub issues.

If you believe this would be useful then I would be glad to write such a document, or at the very least contribute, on weekends where I have the energy to do so.

[ejmr]

@zonuexe I have begun writing a document for this pupose and will push out a branch when I feel it is appropriate. I wil push that branch before the document is finished, but after I feel it is ready for comment and review.