Make travis release wheels on pypi

[EFord36]

Description

Hi,

Would you consider releasing wheels for seqeval on Pypi as well as sdist releases?

Travis only uploads a source distribution ('sdist') by default to Pypi (see here: https://docs.travis-ci.com/user/deployment/pypi/#uploading-different-distributions). Adding wheel as well.

In particular, this would make installing seqeval much easier for me in a specific corporate environment, as at the moment, the fact that seqeval requires setuptools_scm at setup causes pip to execute without a proxy when building seqeval, as the proxy isn't passed through with PEP-517 build isolation - see this issue: pypa/pip#7805 . If seqeval was distributed as a wheel, this would sidestep the issue (as the package would already be built when downloaded).

I believe this PR should be the correct way to distribute seqeval as a wheel using Travis, but I haven't used Travis much myself, so this probably would require testing on your side. Let me know if you would rather me make an issue than a PR if this doesn't work straight away.

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

No testing - it's unclear to me how I can test this without access to the Travis CI for seqeval. If there is some way I can test though I'd be happy to.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules