Removes vim-mode: event prefix

As a supplement to #237, this PR removes the vim-mode: command prefix as we are now using proper jQuery event namespaces via the .vim-mode suffix.  Any custom keymaps people have written will need to be updated, but this eliminates the redundancy of the internal bindings, as they are currently bound as `vim-mode:move-to-mark.vim-mode`.

The path for people to convert their custom keybindings is to remove the vim-mode: prefix in favor of the .vim-mode namespace.  For example, before if you had a binding to move up a row when pressing 'u':

``` coffee
'.vim-mode.command-mode':
  'u': 'vim-mode:move-up'
```

Now it would look like this:

``` coffee
'.vim-mode.command-mode':
  'u': 'move-up.vim-mode'
```

Note that the explicitness of the .vim-mode event namespace is only needed if vim-mode binds to a standard EditorView event of the same name and you only want to call the vim-mode event.  There is no harm in being explicit with the namespace for safety's sake, but it is largely un-needed for keymapping's sake.