Upgrade eflomal

[mshannon-sil]

This PR updates eflomal from 0.1 to 2.0.0 to fix #431, modifies the Dockerfile to use the pip installation of eflomal, and adds eflomal to the ALIGNERS dictionary in silnlp/alignment/config.py permanently instead of only when eflomal is installed so that the error message will be eflomal is not installed rather than invalid aligner.

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This change is 

[isaac091]

Can you tag the last commit so that a new image is built and published?

Reviewed 4 of 4 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @mshannon-sil)

[mshannon-sil]

I removed the change to add eflomal to the ALIGNERS dictionary by default, since that's causing experiments to fail when eflomal is not installed, and eflomal is still just an optional requirement.

[mshannon-sil]

Merged in Isaac's commit which allows for the updated error message without crashing tasks that don't need eflomal.

[ddaspit]

Reviewed 3 of 4 files at r1, 2 of 2 files at r3, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @isaac091)

[isaac091]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @mshannon-sil)