muttrc: update/ set formats

Some adaptations of formats gleaned from Steve Losh's (Homely
Mutt)[http://stevelosh.com/blog/2012/10/the-homely-mutt/]
muttrc: pager stop and uncollapse_jump

More changes from (Homely
Mutt)[http://stevelosh.com/blog/2012/10/the-homely-mutt/]
keybinding: add more `vim' bindings

*   add keybindings file; defines several `vim' bindings (sorely missed)

*   gmail.muttrc has conflicting sync binding; (re)moved to keybindings

*   add source line to `muttrc`