Added method and test for recording a file save

I am adding the modification stamp of the resource.
Added JSON constant for the modification stamp
Added the modification stamp as a parameter to the recorder method
Building the correct JSON object
Added the modification stamp for the refresh JSON
The record method now takes the modification stamp

Also updated the callers.
Extracted the save recording in a new method
Added a map to keep track of file versions
Recoding the version on save

And checking it during refreshes
This method is actually a constructor
This solves a NullPointerException

Due to the auto boxing mechanism which fails when dealing with
a null
Merge pull request #101 from caiusb/save-refresh-double

Save generating refresh problem
Using the variable, instead of getting the same thing again
Removed the file.exists() check

It is useless, because at this stage, the file will always exist, so this will
always return true.
Import cleanup
Merge pull request #102 from caiusb/file-check-remove

Removed file existence check in the FileBufferListener.java