Basic export support; Started other features

TODO: Converters.
- Added basic export support using Blackfriday module. There's also a
  fairly useless passthrough module.
- Add Github API interpreter. (I need internet for that one...)

TODO: Server. (Make it work?)
- Started work on mdview server. Right now it does pretty much nothing.
- Working file path decoder.
- Support for viewing files piped in?
- How to determine if server is running? (Handle a special URL?)
- Where to store server configuration? (Like when to close server,
  delay?)
- Display templates for MD files.
- Some way to modify server settings within browser. (A special form
  embedded in the outputs?)

TODO: Misc.
- Better modularization in the main application code.
- Throw in some unit tests. (It's not a complete go test if you never
  use the test utilities!)
- Add support for batch markdown processing. (It's DEFINITELY not a
  complete go test if you never use goroutines!)
- Try associating the viewer as the default viewer for .md files.
Github interpreter; Server

- Github RAW interpreter was added.
- The server now works, along with a few changable parameters.

TODO:
- Still need templates (and probably need to make sure the server
  specifies text/html as the content type).
- A way to configure the default variables would be nice.
Merged with origin