Implementation of diff file name extension checking for .min and content

checking for a small number of long lines in a file. If either is true then

it is likely a minified file. The minified file is then collapsed similarly

to deleted files and can be expanded to show the content of the file.
In diffviewer/diffutils.py, get_diff_files() performs the file extension

check then in populate_diff_chunks() if the file didn't have a .min

extension the content check is performed.
If the file was previously marked as a min by it's extension and if it has

less than 20 lines total then the lines are length checked to be greater

than 500 characters and if true remarked as minified files.
The diff_file_fragment.html then replaces then diff content with a minified

file message and a show content button that with a event listener in 

diffReviewableModel.es6.js and diffViewerPageView.es6.js loads in the 

minified file contents to the fragment.

test_diffutils.py python test written for testing minification testing.

test_minified_file_detection creates a minified diff object and verifies

the diffutils.py populate_diff_chunks() minification content check.
Ran Python Unit Tests.
Ran Javascript Jasmine Unit Tests.