Update API docs link

Links to latest copy of Phoenix documentation.
Use generic link and remove "building docs"
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
Add :ping and :pong to Phoenix.Socket.Handler.websocket_handle/3

The `cowboy_websocket` module takes care of sending the reply to ping
messages, but then immediately crashes the process by invoking
`websocket_handle`. This change just adds no-op clauses
appropriately.

For future reference, Cowboy also provides a `:binary` tag, which is
currently unhandled.
Merge pull request #449 from nickmeharry/websocket-ping-pong-frames

Add :ping and :pong to Phoenix.Socket.Handler.websocket_handle/3
clarifies wording in the comment for the using block
Merge pull request #450 from lancehalvorsen/clarify-wording-in-phoenix-view-template

Clarify Wording in the Phoenix.View Template