Move WAL interfaces
Merge pull request #1014 from tweise/hds

Move WAL interfaces
Add test for get
Merge pull request #1015 from tweise/hds

Add test for get
Relocate file access mock to test package.
Merge pull request #1016 from tweise/hds

Relocate file access mock to test package.
Merge branch 'hds' of github.com:DataTorrent/Malhar into hds
Use reusable ByteArrayInputStream to avoid creating new stream object
all the time