Records -> Structs

Changed over all records (except one defrecordp, [connection](https://github.com/dynamo/dynamo/blob/master/lib/dynamo/connection/behaviour.ex#L66)) to structs (thanks @alco for helping!).

Using Binary.Dict to get rid of deprecation warning "Using records with the Dict module is deprecated, please use structs instead", maybe this should be extracted out of Dynamo?

Couldn't find what happened to __ENV__.location, replaced with __ENV__.file and __ENV__.line instead in tests.

The following lines still report deprecation warnings:
- test/dynamo_test.exs:40 DynamoTest."test defines root based on otp app"/1
- lib/dynamo/static.ex:45 Dynamo.Static.init/1
Deprecation warning: "String.from_char_list!/1 is deprecated, please use String.from_char_data!/1 instead". These lines do not utilize Sting.from_char_list!/1, error line reporting incorrect?