fixes #637: add remove_storage helper

[Khushiyant]

Fixes: #637

Added remove_storage helper along with following tasks:

• [x] Test unit for remove_storage
• [x] Function Docstring for easy usage

Now, method of deleting the storage records:

 client.remove_storage({'keys': ["entry 1", "entry 3"]})

Successful deletion returns

{ "result":"success"}

[Khushiyant]

@amanagr review requested