Allow -r to run without a full path.

When running diamond in the foreground, it's useful to test single collectors. This functionality already exists, but to extend it:

diamond -f -l -r memorycollector
Will now default to the configured collectors_path and find only collectors that match the name specified.
In this example, if the default collector path is /usr/lib/diamond/collectors and we pass in -r memorycollector, the run_one function will collect all the collectors in /usr/lib/diamond/collectors, remove files that don't match with the name specified in the -r directive, and then execute only those files.
Add rudimentary support for Riemann TTL attribute.
Merge pull request #479 from johnseekins/master

Allow -r to run without a full path.
Merge pull request #480 from ophelan/ttl

Add rudimentary support for Riemann TTL attribute.
Merge pull request #478 from esacteksab/master

WebsiteMonitorCollector -- Gather's HTTP response time, grouped by HTTP Status code
mysql collector now accepts any case version of 'true' for configuration switches
Merge pull request #482 from peterkh/master

mysql collector now accepts any case version of 'true' for configuration switches
Use str_to_bool for mysql config bools, Fixes #483
PEP8
Unused imports
AWS CloudWatch Handler - Supports InstanceID Dimension, requires boto
Merge pull request #484 from anthroprose/master

AWS CloudWatch Handler - Supports InstanceID Dimension, requires boto
Merge branch 'master' of github.com:BrightcoveOS/Diamond
Catch URLError not HTTPError to handle unavailability (e.g. connection refused) AND http errors.

Change-Id: Ic95ee74b7f22251ad25ad1ebfd1f716e453dc7c4
Merge pull request #485 from rtoma/es-fix

Improved exception handling for Elasticsearch collector
Merge branch 'master' of github.com:BrightcoveOS/Diamond
spelling
Broader exception catching for ES collector http call

Change-Id: Ic03c518caf443636d5740680b3d55dae34c8a564
Adding new netapp Disk collector
thread-safety; some refactoring