add folsom_cowboy
add folsom and folsom_cowboy to app list
uses folsom and folsom_cowboy for realtime metrics

The `logplex_realtime` has been gutted and replaced by a couple calls to
`folsom_metrics`.

The `ehmon` dependency has been dropped in favour of adding
`folsom_cowboy` and allowing the metrics to be fetched via a locally
listening port.

In order to fascilitate the addition of `folsom_cowboy`, the `cowboy`
dependency has been updated to the latest 1.0.x cowboy branch. It was
necessary to copy over the now deprecated `cowboy_client` to logplex
src. This should really be replaced by `gun` at some point.
rename all folsom metrics

The metric names now follow the heroku metric name guidelines.
update README with metric information
use a simpler folsom_cowboy branch
gracefully handle body reading failures
Merge branch 'master' into folsom-metrics
bind only to local loopback interface
convert from old metric names to new on the fly

This will make performing a live upgrade easier. The code needs only be
reloaded in various places. As the servers naturally roll and processed
die the old metric usage will drop to zero. Old metric usage will be
logged so that it may be tracked over time.
replace forked `folsom_cowboy` with original version

The fork was initially required to make metric types available as part
of the `/_metrics/[NAME]` API call. Later code splunking unearthed an
undocumented query string parameter `/_metrics?info=true` that makes
that same data available.
handle preexisting metrics
consitent cowboy deps across all rebar configs
deal with cowlib test functions
Provide some more info via logging

  - http_drain response code
  - logplex_api timeout on drain token lookup for nsync/ETS sync
Add request_id to API timeout logging.
I don't like the way this is nested...

But I like duplicating code even less...
Break out nested cases into single function
Whoops. Late night coding leads to mixed up cases.
Ugh. Typo.