Plugins can now create their own commands using the `MakeCommand`
function. Plugins can also now create their own keybindings with the
`BindKey` function. See the go plugin for an example of `MakeCommand`.
This commit puts in place the ability for multiple views (splits).
This commit also removes the editor bindings so that all bindings can be
rebound by the user.
I also added some more comments
This fixes#109
