Support serving precomputed static gzip source files

[plasticine]

Hi there,

I understand that on-the-fly serving of Gzipped source files was removed sometime in 0.11 (in 5ee886b specifically), however I would like to propose that Karma should support the serving of precompiled *.js.gz source files if they exist.

When doing remote testing one of the big stumbling blocks, and the cause of nearly all false-fails is due to the network overhead of serving large test bundles to Saucelabs or similar. For example our main test bundle weighs in at ~20MB without compression (~3MB with compression).

I totally understand why computing and serving a gzip alternative is not ideal in most cases, however using something like connect-gzip-static seems like a reasonable compromise between control and speed.

Cheers,
Justin

[dignifiedquire]

Karma already does a lot of things, and I do not want to add this on top of it. If you really need this, it should be very easy to add sth like nginx or a simple connect server in front of it that gzips files when needed