* Use the official aws-sdk instead of jet3t
* fix compile and serde tests
* address comments and fix test
* add http version string
* remove redundant dependencies, fix potential NPE, and fix test
* resolve TODOs
* fix build
* downgrade jackson version to 2.6.7
* fix test
* resolve the last TODO
* support proxy and endpoint configurations
* fix build
* remove debugging log
* downgrade hadoop version to 2.8.3
* fix tests
* remove unused log
* fix it test
* revert KerberosAuthenticator change
* change hadoop-aws scope to provided in hdfs-storage
* address comments
* address comments