Remove CocoaPods

[jkmassel]

This PR removes CocoaPods, using Aztec and Gutenberg directly.

It builds fine locally, but if you run the app and tap "Posts" it crashes immediately.

Opening this PR for reference as the issue is addressed.

[dangermattic]

Danger has errored

[!] Invalid Dangerfile file: No such file or directory @ rb_sysopen - ./Podfile.lock. Updating the Danger gem might fix the issue. Your Danger version: 9.5.0, latest Danger version: 9.5.1

 #  from Dangerfile:11
 #  -------------------------------------------
 #  
 >  podfile_checker.check_podfile_does_not_have_branch_references
 #  
 #  -------------------------------------------

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