fix(karma-webpack): don't include the file extension (output.filename)

[Havunen]

This PR contains a bug fix

#322

[jsf-clabot]

All committers have signed the CLA.

[michael-ciniawsky]

@Havunen Please sign the CLA

[edmorley]

The appveyor CI run failed due to the NPM DNS issue which should now be resolved. Could someone retrigger? :-)

[ryanclark]

How does this work with entry files that have an extension that isn’t .js? .ts, .coffee etc.

[michael-ciniawsky]

Yeah, its' very weird why [name].js doesn't work with karma-webpack. I was even under the impression the extension needs to present in config.output.filename... Maybe this is a bug somewhere else in the code

[ryanclark]

It turns out the issue was a bit different than the filename having .js in it - I've submitted a PR (#347) that fixes the issues with it. I'm closing this as it's no longer needed, thank you though!