Add feature: tmux tabs and splits open to PWD

Now when you create any type of split or tab, tmux will now
to use the your current diretory in that new tab or split.
creating a new tab with Tmux N key will now open to PWD
Merge pull request #2 from SnJedi/feature/tmux-tabs-splits-open-to-current-directory

Add feature: tmux tabs and splits open to PWD