Use an SVG badge.

An SVG badge looks better on Retina screens and when zoomed in.
Merge pull request #143 from espadrine/patch-1

Use an SVG badge.
removed double import, causes confusion
Merge pull request #179 from gillesdemey/feature-removed-import

removed double import, causes confusion
Update README.md
fixed typo
Merge pull request #252 from 1ace/patch-1

fixed typo