Feature/jsa/more new indexes

* use Content model (to avoid querying mongo with "$in")
* add indexes for non-default sorts
* streamline api code

less user queries

performance.

Add newrelic_moped

This will hopefully give us more insight into mongo performance.

This corresponds to the Gemfile change in a9d281ad.

Allow authentication by HTTP header

Previously, authentication could only be done using a URL parameter,
which appears in various logs. Now, clients can authenticate using a
more appropriate HTTP header.

update to latest newrelic rpm

Revert "Merge pull request #29 from edx/chore/markchang/replace-rvmrc"

This reverts commit d97009d1, reversing
changes made to a9d281ad.

moved to more standard .ruby-gemset and .ruby-version from .rvmrc

Update Gemfile

use ThreadPresenter to render search results

Feature/jsa/new handle threads

additionally, remove unused caching features and update mongo indexing.

remove recursive queries in comment thread views

add simple filtering on inbound content based on a collection of forbidden content bodies