Update CHANGELOG for beta 6

Beta 5

Sigh (pinterest#174)

* Maybe this way instead.

* No longer need the workspace

* Hopefully don't need build

Revert "Revert beta 2 in podspec until we're ready to publish." (pint…

…erest#138)

This reverts commit df836fb.

Update to beta 3.0.1

This is a bettor solution. Thank you @johnezang! (pinterest#98)

* This is a bettor solution. Thank you @johnezang!

* Add a sanity test

* Only delete directory if it exists

Update to 2.2.2

Merge pull request pinterest#71 from benasher44/basher_pincache_2.2.1

PINCache 2.2.1 release