Merge pull request #808 from Microsoft-CISL/juwang-httpServerDistributedShell

Juwang http server distributed shell command

Merging assuming that we will have more unit and end-to-end tests for the web server soon
re-format test files
Merge branch 'master' of https://github.com/Microsoft-CISL/REEF into juwang-httpAvroSerilazer
adding negative test cases for AvroHttpSerializer