Merge pull request #7 from yuhei-a/master

Change: image #optim() #optipng()
Merge pull request #8 from yuhei-a/master

Update: test-image
release: 0.9.8
Add: pngquant support
Add: constant imagemagick#convert
Fix: check used optim
release: 0.9.9
Update README.md
Fix: png compression does not come into effect either
Merge branch 'master' of github.com:CyberAgent/beezlib
release: 0.9.10
Add: package.json keyword
Change: stdout/stderr to debug mode
Bugfix: cannot turn off jpegoptim by `options.jpegoptim.use`
Merge pull request #9 from t93/master

Bugfix: cannot turn off jpegoptim by `options.jpegoptim.use`
release: 0.9.11
fix contributor url
Fix: enable to change base ratio
Merge pull request #10 from CyberAgent/fix-ratioresize

Fix: enable to change base ratio
Update: docs
release: 0.9.12