Use resourceful routes for terms view/accept/decline

[AntonKhorev]

• make user terms a nested resource inside the account resource
• GET /user/terms changed to GET /account/terms. It's inconvenient to have it at /user/terms because that depends on the declaration order. If user resources are declared first, they capture terms as a username. I still add a redirect from /user/terms to /account/terms which has to come before resources :users, but with redirects it's obvious that they are temporary.
• POST /user/save changed to PUT /account/terms. With user#save it's not clear that this is a target of the terms form.

[gravitystorm]

Looks good to me, one small change in the tests.

I also appreciate the tests are slightly refactored, and this is an improvement.

[gravitystorm]

Merged, thanks!