clean up of code per joe p's request
Adding 'Opportunities Volunteered For' to profiles.

Previously, the profiles only displayed opportunities created by
the user. Now there is a seperate list for opportunities that
the user has volunteered for.

Fixes #234
fixed typo
Don't show volunteer button if not logged in

Fix my own regression -- the user object should not
be set to anything if it doesn't exist.  In the template,
guard against an empty user object.

Fixes #253

Reverts 337d4a5b740ed2ebaa03ca2c3f5e747fe453019e
Merge pull request #254 from 18F/hotfix/task-volunteer

Fixes the problem for me. Merging it in.
Merge pull request #245 from brandtheisey/devel-opp-tag-fix

Inline Tag Creation during Opportunity Edit and Creation Cleanup
Merge pull request #246 from DavidEBest/devel-volunteer-opps

Adding 'Opportunities Volunteered For' to profiles.