[important] Change license of Emperor to BSD

All files were changed to a BSD license and some functions were changed
as a consequence of this.

Can the following authors respond whether or not they agree with the change of
licensing for this software.

- [ ] @gregcaporaso
- [ ] @meganap
- [ ] @justin212k
- [ ] @antgonza
- [ ] @jacksonchen
- [ ] @jrrideout
- [ ] @danknights
- [ ] @clozupone
- [ ] @rob-knight
- [ ] @RNAer
- [ ] @eldeveloper

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I'll check the boxes as people respond to this message.