This is both more correct and also fixes this element having had a
name very similar to message_control_button, which refers to an
element in the message_controls section of a rendered message.
We move compose.html to compose.hbs file while keeping
`#compose` still in `home.html` as a hanger
where append rest of the elements.
This will provide us with two benefits:
* We could share common elements between message_edit_form and
compose.
* We can insert compose directly in any element. We may decide to
do it for recent topics.
Aman Agrawal