Fix UMD build

#### 1/3 PRs resolving https://github.com/marionettejs/backbone.marionette/issues/1264

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**Changes:**
- Move umd build to `src/build` files
- Add bare build
- AMD: Remove unused exports object from dependencies

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You'll want to look at this without the white space changes

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[See built lib files here](https://gist.github.com/thejameskyle/ecde48a3cce63c2e1aa4)