Use SVG badges instead of PNG badges

SVG badges look beautiful on retina displays.
Remove node_modules from .npmignore

More information:
https://www.npmjs.org/doc/misc/npm-developers.html#keeping-files-out-of-
your-package
Merge pull request #33 from shinnn/master

Use SVG badges / Fix .npmignore
3.0.1
Merged from orginal (v3.0.1). Fixed tests