First changes to add REPL to CLI

Added Liner package, add execution code
Implementation of REPL mode

added global replMode
cli_helpers changed to be less aggressive
accounts:info tested modified requirearguments (change still needs to
be made for all other commands)
extended autocomplete to include help command autocomplete.
Go fmt & Go vet fixes - Added keys to CLI flags
Add LoginController pre-auth
Also put in terminal close deferred.
Most controllers exit on errors. Modified so the exit unless replied is set.
Also added replExit flag to allow soft exits from real to recover terminal.
Extracted repl code to own file

Moved repl code and vars out of the main file and into own file
PR fixups

Rebased,
dryed the osexit calls
made base_controller/prompt repl aware
to invoke repl, symlink binary to mongohq-repl and run that
Change to shell command, fix ctrl-c bug
Ctrl-C now resets terminal properly
Converted shell to an actual subcommand
Merge pull request #19 from MongoHQ/replicas

Replicas