preventDefault all keydown events

Stops interrupting keybinds such as quick find in Firefox.
Add pasting
Fixed more broken key events in Firefox
Add moving/copying

Fixes #9 (maybe; may not be the best solution)
0c6aef26b913b34fae99b9c13233e59dd57013b6 also fixed #12
Add Ctrl+r, Ctrl+s, Ctrl+t

Fixes #7
Revert "Add moving/copying"

This reverts commit aa47094b2ea0deefbdefc0b5cf6f859d4c71bd22.
Remove some redundancy
Merge pull request #23 from Imgoodisher/master

Pasting, Ctrl r/s/t, more Firefox broken key events