move tinypng.sh to your project root

Fisrt, install jq to parse json,brew install jq in mac.

Then, just run ./tinypng.sh .

1. All png files in this project will be compressed by recursion。

A key can compress up to 500 png for free. Support multiple keys to slove this problem,premise is you have multiple mail to apply key.

Support record which files are compressed, and then skip these files.