iOS fixes + cleanup

[mojodna]

The duplicated getAll method was causing the React Native bridge to fail when it couldn't resolve which target to use.

This also cleans up cookie list generation to use the helper that already existed (createCookieList) and adds (optional) expiration date formatting to it.

[mojodna]

Incorporates #124 and fixes #120 (using a different approach than #121).

[basudz]

@joeferraro I need this in master, can you merge this please?

[jpamarohorta]

Thanks for the fixes, working perfectly.

[safaiyeh]

I have forked the repo here: https://github.com/safaiyeh/react-native-cookie-store We can create issues and PRs there to continue the development of the project.