Fix concatenation for URIs, update Gem to latest deps, fix spelling errors.

Hi there,

I'm trying to use this in a Rails app, but the scopes on authentication URIs seem to be misshapen. Rails throws `URI::InvalidURIError (bad URI(is not URI?)` using the 0.0.2 version.

I fixed it by concatenating them with '+', got it to get both the OAuth request code and the access token with these changes. And I've updated the tests, and fixed a spelling error with them that threw a couple of failures.

And I've took the liberty of updating the gem's dependencies, feel free to request a new PR without this (or anything you see that looks off).

Apologies about the evasive diff, something must've gone wrong on the way to Github, it only diff'd the lines I changed on my machine! :smile: