Fix opam lint requirements

Merge pull request #121 from darklang/paul/fix-opam-0.0.7-release

Don't use int_of_string_opt, which wasn't available before OCaml 4.05

Merge pull request #48 from darklang/release-0.0.6

Release 0.0.6

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Note deployment docs

remove "str" in response to opam code review