Add Bulk Giving Page

[jeresig]

The URL structure for the page should look something like this:

https://www.gittip.com/give/?
    user[0]=jeresig&
    on[0]=github&
    amount[0]=0.25&
    user[1]=wycats&
    amount[1]=1.0&
    title=jQuery Dev Team&
    desc=These are the people who make jQuery, give us money!

The query string uses the array-style format for all the fields. Each field works as follows:

• user: The username of the user.
• on: The service the username is for (default: gittip)
• amount: The amount of money to give to this user (in dollars)

If an 'on' is specified for a user then the username should be automatically resolved to a gittip username, if possible.

Additionally there are two optional params:

• title: The title to give the page
• desc: A description, or explanation, to give the user explaining what it is that they're supporting.

The result of visiting this URL should look very similar to the proposal for the new organization contribution page (with the title and description replacing the associated title/description, see #877).

[chadwhitacre]

P.S. I'm brain-dumping on this and related issues over on #877.