Rename `res.sendfile` to `res.sendFile`

[see https://github.com/strongloop/express/pull/2266]
build
Global rename sendfile => sendFile
build Closes #193 #175
Remove sendFile from 3.x Closes #196
Fix sendFile example Closes #197
Mention res.sendFile absolute paths
Fix typo

Per https://github.com/strongloop/expressjs.com/issues/157
Remove broken link per issue 173

https://github.com/strongloop/expressjs.com/issues/173
Fix grammar
build for #163
Update app-VERB.jade

In this case, "where" is correct, not "whereas".
rescrubbed copyright
updated GA tag