feat(test): add raw browser testing

[douglasduteil]

Following #46

I made a horrible hack that reinstall jspm@beta again... but it works :) I'm a really open to any alternatives :pray:

Cheers :beer: @guybedford

[douglasduteil]

It's a really naive approach :blush: I will obviously better to

• not install jspm@beta 3 times (on the cli)
• not install tape 2 times once with npm once with jspm

[guybedford]

To avoid installing jspm 3 times, we could just have it installed at the base-level node_modules for running both the build and tests.