More csrf-token stuff.

--HG--
extra : rebase_source : 87a0f590ce45de38d2a67d3b2ba7a630262bd53c
Use form_tag helper to generate csrf token field.

--HG--
extra : rebase_source : a2293e44d861d0197166c639569c52116cbf14a6
Another csrf token form stuff.
Yet another form csrf stuff.
Confusing "pretty name".

Especially when the underscore is located at the end or beginning.