Losslessly compress the shields.io images.

Before: 91,1 KB (93.363 bytes)
After:  66,4 KB (68.036 bytes)
Merge pull request #125 from XhmikosR/update-deps

Update dependencies.
Merge pull request #126 from XhmikosR/compress-img

Losslessly compress the shields.io images.
Update dependencies.