Merge pull request #52 from jochenberger/remove-unused-jsonprovider-methods

remove unused methods from `JsonProvider` interface
Applied Gson patch and added Gson converters for List and Map.
Fixed constructor in ConversionException
Need Java 1.7 for Heroku web app.
Added travis file
Added travis build info icon to README. Removed release history.
Merge remote-tracking branch 'upstream/master'
remove `System.out.println`
Merge pull request #55 from jochenberger/cleanup-gson-provider

remove `System.out.println`
Merge remote-tracking branch 'upstream/master'