Create Pull Request and Issue Templates

[capnkenny]

As part of the discussion on #384, we'll want to add pull request templates and issue templates. This will do the following for us:

• Allows us to become more uniform in quality with open Issues / Pull Requests
• Allows us to better provide examples to the community on what we expect when opening an Issue / Pull Request
• Allows us to define what is versus is not allowed to have a Pull Request without an existing Issue opened (looking mainly at code/functionality changes versus just a documentation change)