Add support for Eucalyptus endpoints

- Add facade for constructing AWS service clients w/ configured endpoints.
- Add properties for setting AutoScaling and CloudWatch endpoints.
  com.netflix.servo.aws.endpoint.cloudwatch
  com.netflix.servo.aws.endpoint.autoscaling
- Construct clients using facade in CloudWatchMetricObserver and
  AwsInjectableTag.
Merge pull request #189 from eucaflix/eucalyptus

Add support for Eucalyptus endpoints
Introduce a new datasource type = RATE
Fix StepCounter and PeakRateCounter
Merge pull request #190 from dmuino/rateType

Introduce a new datasource type = RATE
Update javadoc and default sampleSize for statTimers
Merge pull request #193 from dmuino/statsTimer

Update javadoc and default sampleSize for statTimers
[Gradle Release Plugin] - pre tag commit:  '0.4.45'.
[Gradle Release Plugin] - new version commit:  '0.4.46-SNAPSHOT'.
added BucketTimer
Merge branch 'master' of https://github.com/brweaver/servo
updating BucketTimer as per code review
Merge pull request #196 from brweaver/master

BucketTimer merged. Thanks!
[Gradle Release Plugin] - pre tag commit:  '0.4.46'.
[Gradle Release Plugin] - new version commit:  '0.4.47-SNAPSHOT'.
Add a counter to the EchoServerExample
Do not throw on increment with invalid tags
Merge pull request #200 from dmuino/dyncounter

Do not throw on increment with invalid tags
[Gradle Release Plugin] - pre tag commit:  '0.4.47'.
[Gradle Release Plugin] - new version commit:  '0.4.48-SNAPSHOT'.