Add keepalive to grunt file for test server to work
Remove Jquery Promise and replaced with es6 Promise

- make sure all test pases except jquery integration.
- when es6 Promise.promise was parsed in to $.when , it did not wait for
  promise to resolve and return the value
Added a thenable integration to replace jquery integration test
remove keepalive in grunt because of travis ci. Added jasmine-server grunt task
Updates Add function to use es6 promise
Updated update function to use es6 promise
Updated most of the function to use es6 promise
Updated open function to use es6 promise
Updated the description of spec to use promise
Updated README to replace jquery promise to es 6

- updated contribute note
Merge pull request #79 from wizztjh/es6-promise

Es6 promise