Preserve folder structure during build

[farism]

Fixes #717

By default babel only copies *.js files when passing in a whole directory. Instead of globbing for *.js files, just pass the entire sourceDir as input and configure babel to also ignore node_modules. This should preserve the folder structure.

I went to remove glob as a dep but couldn't find it listed as a dependency anywhere.

[istarkov]

Thank you

[barbalex]

is it possible to quickly build a new npm version so people don't stumble over this when updating?

[barbalex]

Weird thing is: This page does not have v28 in the releases. But v28 is latest on npm and that is what you get installed - which then errors.