Added Hipchat extension
check-stats.rb: fix the issue of nil datapoints

Sometimes Graphite is lagging a bit. When that happens, the last data point in some (or all) metrics collected by this plugin will show as nil.

When calculating the average, nil is treated as zero. That throws the calculation out of balance. I've seen cases where the real metric was just a tiny bit over the threshold, yet it would not trigger the warning because the average was lowered by nil data points. I've had instances when that would continue for a long time, effectively masking the warning or the critical condition for up to 30 minutes, which is unacceptable.

For that reason, in the danger() function I've changed datapoints = metric['datapoints'].blah to throw out the nil points. Then the nil points are not artificially lowering the average anymore.

That's the first part of the diff.

The 2nd and 3rd part of the diff are related to the situation when all datapoints (not just the last one) in a metric are nil. In that case, the true status of this plugin is 'unknown', because that's what it is - we don't have any actual data points (they're all nil, which means missing data), so we acknowledge the 'unknown' status.
Fail with unknown state if not running with elevated privs
Changed apikey to room_api_toekn for clarity
add check-ec2-network.rb
delete blank line.
Updated to use new Twilio API
Allow server URL to be customised for hosted hipchat server
remove duplicate fields
Add a check for rabbitmq cluster health
Create memory-metrics-percent.rb

Based on memory-metrics.rb, but with output in percentages instead of absolute values.

Instead of adding percentage output to memory-metrics.rb, I was told it's better to create a new plugin. So here it is.
Delete memory-metrics-percent.rb
Create memory-metrics-percent.rb

Like memory-metrics.rb but with output as percentages instead of absolute values.

I've tried to merge these changes into memory-metrics.rb but I was told it's best to create a new plugin instead. So here it is.
Add configuration parameter to OpsGenie handler.
Added SSL support for pulling haproxy stats
Add librato-metrics handler setting to set the sensu client hostname as source when reporting to librato
Update check-disk-fail.rb

Didn't work with embedded ruby with #!/usr/bin/ruby. Fixed it.
Adds new metric to keep track of a file's size
Fixes some syntax issues reported by RuboCop
Merge pull request #811 from tas50/master

Fail if not running with elevated privs, alert on warn state, fix wording