I've suggested in
MDL-39092 that we should upgrade our recommend Shifter version to 0.3.1.
I think it's wise to update to the latest version of the tool before each release, and this version will introduce some changes to the built files - namely, that the coverage files are minified.
Additionally, the code coverage tool in Shifter has been changed to Istanbul which is a pure-JS tool. The previous versions of Shifter used yuitest-coverage which required Java.
Minifying the code coverage should help make diffs more readable too.