Updated podspec version

updated podspec

Merge branch 'immutable-mappable'

Updates to readme

updated signing settings

- updated compiler warning settings

Merge pull request tristanhimmelman#459 from Hearst-DD/mappable

Mappable

Merge pull request tristanhimmelman#403 from pixel4/add-nullable-from…

…-json

Add the ability to reset object properties to `nil` from JSON

Merge pull request tristanhimmelman#392 from Hearst-DD/bitcode

Bitcode

Enabled bitcode for watchOS and tvOS