Fix servlet docs.

Closes #424.
avoid NullPointerException when second argument to name function of MetricRegistry class is null
add test for name function of MetricRegistry class when names is null
Pin to my new GPG keypair.
Merge pull request #426 from djsutho/patch-1

avoid NullPointerException in name function of MetricRegistry class
Reporters implement Closeable
Merge pull request #430 from ryantenney/closeable-reporters

Implement Closeable interface in reporters
CvsReporter -> GangliaReporter
Merge pull request #433 from jplock/patch-1

CvsReporter -> GangliaReporter
Fix handling of async requests.

Fixes #435. Closes #436.
Fix Counter javadoc.

Closes #434.
Alter Cormode paper link
Make documentation link to Cormode paper
Added new constructors to HealthCheckServlet and MetricsServlet

Making it possible to assign registries via constructor rather than via
ServletConfig.
Useful for programmatic embedding and test scenarios.
Add CORS Access-Control header.

Have the MetricsServlet send back the Access-Control-Allow-Origin header
so that the JSON output from the metrics servlet can be used in browser
based dashboards separate from the application.
Fix Gauge javadoc

The gauge docs incorrectly list value instead of getValue
Add test for Meter EWMAs approximation
make sure that EWMA intervals are adjacent
Merge pull request #442 from jmslagle/patch-1

Fix Gauge javadoc
Merge pull request #439 from ceetav/low_rates_ewma

Meter: EWMA deviates for low rates from the actual rate