Last Documentation cleanups for `v5` release (#291)

* Updated MIGRATION_GUIDE.md after changes to Token and Parser

* Updated doc

* Cleanup of README and refer to project page

* Update MIGRATION_GUIDE.md

Co-authored-by: Michael Fridman <mf192@icloud.com>

* Wrapping markdown files at 80

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Co-authored-by: Michael Fridman <mf192@icloud.com>