Moves tab management keystrokes from magic to smash keys

The [magic] + [arrow keys] are used by most window management utilities most notably 'ShiftIt' and are in direct conflict with the current RM tab management key bindings.   This commit moves those bindings to be [smash] + [arrow keys] which does not have any known conflicts with anything allowing developer to be able to manage RM tabs using keybindings again.

Glossary:
magic = [ctrl] + [option] + [cmd]
smash = [magic] + [shift]
Merge pull request #12 from codeword/tab_management_fix

Moves tab management keystrokes from magic to smash keys