Updated mix version number to 0.4.1

Fix crash when attempting to atmoize atom keys - https://github.com/EthanML/key_tools_ex/issues/3

atomize_keys no longer crashes if given atom keys

Update version number in README to latest.

Added CodeClimate badge to README

Merge branch 'dev'

Added CodeClimate config file

Updated README with contribution instructions.

Ignore nested Structs - https://github.com/EthanML/key_tools_ex/pull/1

Ignore nested Structs - https://github.com/EthanML/key_tools_ex/pull/1

Merge pull request #1 from benfalk/master

Ignore Struct Keys From Being Stringified

Added docs for lower camel conversion

Updated version metadata and README func list

Extract / DRY map transformers slightly