Pwned Passwords Versions Save

• Resolves issue where panic could occur if response from upstream wasn't as expected (https://github.com/mattevans/pwned-passwords/pull/11) - @WilliamNHarvey

Refactor

• Reduces footprint
• Removes confusing service architecture
• Allows setting of custom HTTP client
• Removes internal store (cache)
• Updates tests

• mod tidy
• travis ver bump

• Removes the handrolled cache/store
• Replaces removed store with a wrapper around patrickmn/go-cache

• Includes support for Go Modules

First release