Loosen gem deps & minor fixes

[paulmakepeace]

Fix up various warnings.

Addresses #39

[eherot]

Heyyyyy any thoughts on getting this merged one day?

[mgrebenets]

Apologies for the "bump it up" comment, but I'm also one of the people who can't wait to see it merged :)

Just discovered https://github.com/clayallsopp/readme-score gem, which depends on unirest. So when trying to get it installed with fastlane version 2.59.0 I get same dependencies conflict.

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