convert `iterm2-borderless` to sha256 :no_check

This is the only usage of `no_checksum` in this repo.
Merge pull request #4 from rolandwalker/convert_no_checksum

convert `iterm2-borderless` to sha256 :no_check
Add EasyTAG 2.1.8-mac-alpha-1
This is not an official build.
Merge pull request #6 from hugoh/easytag

Add EasyTAG 2.1.8-mac-alpha-1