omg-attrs

https://github.com/omgreenfield/attrs

- Adds `Object#attrs` method for querying nested attributes - Adds `Array#where` to return a subset of elements matching a condition - Adds `Array#find_by` to return the first element matching a condition - Adds `Object#matches?` to check if an object matches a condition - Adds `Hash#method_missing` to allow {a: 1}.a instead of {a: 1}[:a]