Update API docs link

Links to latest copy of Phoenix documentation.
Use generic link and remove "building docs"
Add put_view and support atom templates
Use :layout instead of :within and guarantee assigns are maps
Start moving more functions to Phoenix.Controller
Configure the logger level instead of the backend one
Move redirect/2, html/2, json/2 and text/2 to controller
Add support to accepts/2 for mime negotiation
Explicitly generate pipelines in new apps
Remove old content type functionality
Improve docs for accepts/2 and router
Add put_layout_formats/2 and layout_formats/1
Update to latest Elixir
Merge pull request #442 from phoenixframework/jv-controllers

Improvements to rendering/layouts
Update CHANGELOG
Changed atom to parameter variable. Per lib/phoenix/socket.ex#assign/3, the first parameter must be a %Phoenix.Socket{} struct. Sending an atom will cause an error to be raised.
Merge pull request #446 from mgwidmann/readmetypo

README.md code typo
Merge pull request #430 from edubkendo/patch-1

Update API docs link
fixes typos and small grammar issues
Merge pull request #448 from lancehalvorsen/grammar-typo-fixes-for-router

Fixes For Typos and Small Grammar Issues