AWSCredentialsProvider for s3-extentions

- fileSessionCredentials property is added
- AWSSessionCredentialsAdapter is adapter class between aws sdk AWSCredentialsProvider to jets3t Credentials
- FileSessionCredentialsProvider will refresh its session credentials from the file
- S3StorageDruidModule should return different AWSCredentialsProvider on the config settings
A few fixes

- EasyMock instead of Mockito
- FileSessionCredentialsProvider fields should be volatile
- getRestS3Service should create AWSCredentials not a AWSSessionCredentials with fixed credentials
License header and utf-8
update refresh manually every hour
refresh thread should be daemon
Add way to skip determine partitions for index task

Add a way to skip determinePartitions for IndexTask by manually
specifying numShards.
Properties.load instead of manual population
Merge pull request #629 from metacret/ISSUE-628

AWSCredentialsProvider for s3-extentions
Merge pull request #642 from metamx/numShards-IndexTask

Add way to skip determine partitions for index task
upgrade to jetty 9.2.1

Upgrade jetty version
- supports Java8
- Async I/O Proxying
- other jetty bug fixes
Merge pull request #643 from metamx/upgrade-jetty

upgrade to jetty 9.2.1
[maven-release-plugin] prepare release druid-0.6.129
[maven-release-plugin] prepare for next development iteration
Fix race in RemoteTaskRunner that could lead to zombie tasks.
Merge pull request #644 from metamx/rtr-bugs

Fix race in RemoteTaskRunner that could lead to zombie tasks.
[maven-release-plugin] prepare release druid-0.6.130
[maven-release-plugin] prepare for next development iteration