A few changes for consideration

Hi, I have made a few changes for your consideration.

1. include evernote sdk as submodule. This is easy to update and manage.

2. add *getNoteByGuid* function. Essentially, only the **guid** is needed to retrieve a note from evernote server. In this way, we can add a `evervim/bookmark` source for notes you edit often. It is quite annoying to do a slow query each time.
 
3. minor changes to highlight update successful message