refactor: run build on post-install instead of pre-publish

[EzraBrooks]

Fixes #2884.

Switching the bundling to happen on the client-side makes Karma development more flexible. For instance, on projects at work we pull npm packages based on git tags, since we don't have enough to warrant running a private npm registry. If we were to fork Karma, it wouldn't work at all due to the bundling being done on pre-publish.

Additionally, it allows developers to easily pull in pre-release versions of Karma to test locally, since they won't have to manually run the build script when installing the module into a test package.

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[EzraBrooks]

I signed it.

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[EzraBrooks]

Worth noting that I think maybe a more elegant solution would be to compile the client-side resources when Karma spawns the web server for the first time, but this was the easier and quicker way to get my project working again.

[dignifiedquire]

In the past postinstall steps have been very problematic with npm unfortunately, so I always try and avoid them. Not being able to use master out of the box is not great I agree. Doing the browserify run on first start and then caching the results would be the best way to go I think.

[EzraBrooks]

Okay, I’ll close this PR and work on solving it that way instead.