Scaffold the doc command

Add a main module plus menus and keymaps files, doesn't do anything yet.
Change structure to include index.coffee

This seems to be the suggested documented structure.
Change menu to be context menu

No sense having context-free command for doc singe it always pertains to
a workspace location
Change keymap modifier to ctrl-alt

It seems shift doesn't work, it just types a delta character.
Implement launching repl and talking to it

For some reason I can't use Bufferedprocess to do this, piped stdin
doesn't seem to work.
Run repl in project dir
Show docs in split view

View stuff heavily inspired by https://github.com/rgbkrk/atom-python
Reuse doc view for future invocations
Put output in code in pre

This gets rid of linefeeds in funny places
Display doc for word under cursor or selection

Still a bit buggy in that it can screw up the repl state
Encapsulate repl in a class