lcov is reporting coverage against webpack transpiled modules rather than actual source code

[ijsnow]

[felixfbecker]

I think this is an upstream issue: https://github.com/mattlewis92/karma-coverage-istanbul-reporter/issues/40

[felixfbecker]

The same issue caused the same problem in the webapp, and I solved it by switching to browserify + tsify + babelify + babel-istanbul. Should experiment with that.