Add plugins for toggling things

The 'toggle' plugin toggles words like true, false, yes and no. The
togglelist plugin adds mappings for toggling the quicklist and location
list. I might end up editing the former a bit to suit my needs but they
both seem pretty useful as they are!
Add a SpeedRead command to "speed read" the current file

This passes the current file to the speedread program, similar to the
Spritz speed reader. If you're using vim in the console it'll run it
there, otherwise it'll open up a new xterm window because I haven't
found a nice colourful terminal solution for Gvim.
Add ",sr" mapping for SpeedRead

In the short while I used this I realised it's a lot of typing just to
start reading something. Problem solved.