Feature/ctrl backspace

[aaxu]

Finally got around to figuring this out. I've only tested this out on Ubuntu 18.04 since I currently don't have access to a Mac, though I will by next week. More testing would be appreciated but here's a quick look at what I have so far.

Main points:

• The program should be able to handle ctrl_backspace differently from other backspaces (ie Backspace, and CTRL_H)
• This feature should not work on macOS because of security issues, and it should simply behave as a normal backspace.
• This feature should not work if there is no X server running, so it may crash when accessed over an ssh server (needs testing)

[aaxu]

Update: Program should no longer crash when there is no X server available. It will act as if this feature did not exist and CTRL_Backspace should just be a normal backspace.

[aaxu]

I've just removed the parts using pynput, keeping only the functions that support backspacing a word. Currently, there will be no way to actually activate this function since it isn't mapped to any key combination.