readme.md in invoker-1.4.1 vs readme.md in invoker-1.5.1

- old
+ new
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 Invoker is a gem for managing processes in development environment.
 
-[![Build Status](https://travis-ci.org/code-mancers/invoker.png)](https://travis-ci.org/code-mancers/invoker)
-[![Code Climate](https://codeclimate.com/github/code-mancers/invoker.png)](https://codeclimate.com/github/code-mancers/invoker)
-[![Coverage Status](https://coveralls.io/repos/code-mancers/invoker/badge.png)](https://coveralls.io/r/code-mancers/invoker)
-[![Dependency Status](https://gemnasium.com/code-mancers/invoker.png)](https://gemnasium.com/code-mancers/invoker)
+[![Build Status](https://travis-ci.org/code-mancers/invoker.svg)](https://travis-ci.org/code-mancers/invoker)
+[![Code Climate](https://codeclimate.com/github/code-mancers/invoker.svg)](https://codeclimate.com/github/code-mancers/invoker)
+[![Coverage Status](https://coveralls.io/repos/code-mancers/invoker/badge.svg)](https://coveralls.io/r/code-mancers/invoker)
+[![Dependency Status](https://gemnasium.com/code-mancers/invoker.svg)](https://gemnasium.com/code-mancers/invoker)
 
 ## Usage ##
 
 First we need to install `invoker` gem to get command line utility called `invoker`, we can do that via:
 