Feature: Allow C-h, C-j, C-k and C-l to be sent to terminal

Previously these keys would not be able to be used for key mapping in the shell
because they would be intercepted as window navigation key combinations.
However, if we're not in vim, and our tmux window only has one pane, there's no
reason that we can't let these key combinations through.

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Actions:
  Closes #11

Signed-off-by: Jeff Felchner <accounts+git@thekompanee.com>