Rename stage/dev servers to "send.stage.mozaws.net"

[pdehaan]

Per #7 (comment):

@pdehaan says: "Does this mean we want to rename the stage/dev servers from something like https://fileshare.stage.mozaws.net/ to https://send.stage.mozaws.net/?"

@clouserw says: "urgh. Sorry @relud -- how hard is it to change these now? If it's difficult or bad timing it doesn't need to happen right away."

[pdehaan]

Once this is done, we'll need to update (at least) the README.md file and public/contribute.json file (after/if #148 lands).

[pdehaan]

Me thinks this is done. Closing.

[relud]

this is still blocked on #167 before it's fully done