Register deserializers, view providers, and commands in Atom constructor

Previously, these registrations were scattered all over the codebase and
required that `global.atom` be defined, which creating weird ordering
issues. Registering them all from the global makes the relationships
clearer and means we don’t have to assign a global to set up a fully-
functional environment.

src/text-editor.coffee

@@ -54,8 +54,6 @@ GutterContainer = require './gutter-container'
 # soft wraps and folds to ensure your code interacts with them correctly.
 module.exports =
 class TextEditor extends Model
-  atom.deserializers.add(this)
-
   callDisplayBufferCreatedHook: false
   registerEditor: false
   buffer: null