Simplify our mission

The mission/vision statement is verbose. This change boils it down to its essence:

> Gittip's mission is to enable an economy of gratitude and generosity.

I dropped the freighted word "redeem." The verb is now "enable." Rather than defining ourselves in terms of an existent monolithic "economy," I would prefer that we define ourselves in terms of ourselves. My goal is to practice gratitude and generosity. I want to give away my labor as a gift. I don't want to charge for anything I do. Gittip enables me to do that. Other economic arrangements are orthogonal, irrelevant. The baseline criterion of Gittip's success is whether I personally can use it to give money to people and teams that I believe in. The topline criterion is whether I personally can pay my bills from money I receive on Gittip.