Don't set rawValue for a case if it is the same as it's name

[RomanPodymov]

Hello.
Thank you for this utility. It saves a lot of time.
In this pull request I fixed #98.
Before:

enum CodingKeys: String, CodingKey {
    case anyCase = "anyCase"
}

After:

enum CodingKeys: String, CodingKey {
    case anyCase
}

Updated gems.

[RomanPodymov]

Hello @insanoid
Thank you for your approval. But I see that I set wrong target branch for this pull request, it should be dev, not master. Should I create a new pull request to dev with these changes?

[insanoid]

It's fine for now, I forgot to set as default. I will just make a new release.