Browserify v5 support, update tests, and add some comments

Update tests so they all pass for browserify v5.10+ ; note that fullpaths: true must occur (there is probably a way around this but we can do it in a future version). Note this also version bumps to v4.0.0 respectively.

require(entry) does not apply transformations anymore in browserify for some reason; I am not sure if this is a bug or intended behaviour, that is why I moved the entry points into the main browserify function in tests. Fixes #78