Move umd build to dist/atlaspack.js

[rymohr]

With ES6 adoption growing fast it's nice to have the original source. The current approach results in errors like the following in webpack:

WARNING in ~/atlaspack/index.js
Critical dependencies:
1:440-447 This seems to be a pre-built javascript file. Though this is possible, it's not recommended. Try to require the original source to get better results.
@ ~/atlaspack/index.js 1:440-447

May I suggest moving the umd build to dist/atlaspack.js instead?

Related to https://github.com/shama/atlaspack/issues/8

[shama]

Sounds like a good idea.