Helm keybindings - 2nd PR

Reimplementing this commit based on the changes discussed in #71 merged to the latest HEAD

* Added helm-mode to `use-package` idle timer to speed up opening
* Prefixes:
"r" prefix signifies showing buffer data:
 - e = evil-registers
 - y = yank / kill ring
 - m = mark ring
 - r = helm-registers

"f" prefix signifies file activies
 - h = helm-find-files

"F1" default tied to help, so now is `helm-apropos`