API v2 improvements

[crertel]

Some things to make front-end dev life easier:

• updated_at wants to be RFC3339 in UTC so frontend devs can just throw it into a new Date() and get something useful
• updated_at -> updatedAt
• phone should also have cleanPhone which is just the concatenated digits for phone numbers (may be wrong on this)
• supply_needs and volunteer_needs should be merged into needs, and be an array of strings (reducing parsing reqs on frontend)