Switch to radio buttons for pledge

Some bugs yet, and needs cosmetics
Defaults work.
Tweaks to radio pledge, logging
more clear wording on pledge page about share matching
Switch to radio buttons for pledge

Some bugs yet, and needs cosmetics
Defaults work.
Tweaks to radio pledge, logging
rebasing (attempting for first time) the radio stuff up to newer master
Merge branch 'radio' of github.com:dlthomas/snowdrift into radio

Conflicts:
	Model/Shares.hs
fixed merge errors I missed before
Squishy JS for share radio buttons.
Persisting share options in session, dropped 16
mostly adjusted to suggest git fetch instead of git pull
minor GUIDE edits
more clear pledge form and wording, and moved to top above history and
stats
adjusted pledge form further, more clear test message
fixed typo in user summary of pledges
fixed indent error
fixed typo in div syntax
adjusted figures not to be centered when they are within comments