Add explicit MIT License to source dist

[pmlandwehr]

Hey-lo,

I'm building a version of portend using conda for conda-forge. When possible, we try to include a link to the license file in the meta.yaml specification for the build; doing so requires an actual license file be bundled with the dist and (usually) that said license be indexed in an explicit MANIFEST.in file so that it gets included in the source distribution.

Would you consider adding a full copy of the MIT License to the bundle, along with an appropriate manifest?

[jaraco]

Hi. Per jaraco/skeleton#1, I avoid bundling a license file. I recommend that the builder recipe for conda-forge could rely on the license declared in the metadata either to bundle the license at build time or to rely simply on the license declaration in the package metadata.