Check only if sum exceed 12
Updating tests based on the new behavior
Merge pull request #955 from GProulx/ErrorOnlyWhenOver12Columns

Bootstrap: Error only when over 12 columns
Merge pull request #957 from am11/master

Gifsicle: Updated to v 1.83 (Windows)
CssSourceMap: Better use of Linq.
Code: Refactored bundles file watcher.
Code: Suppresses CA1812; class's for JSON decode.