Return points to backers of winning ideas

As per Issue #127 users that back an idea can receive their karma back
once the idea has gone live. This should encourage people to vote more
often and for ideas they like and believe have a chance of being
implemented. This should discourage vote spamming through a limited
amount of votes while still rewarding users for their involvement.
Merge pull request #131 from sdorunga1/adjust-karma-reward

Return points to backers of winning ideas