Integrate code coverage with coveralls.io

[sveneh]

We're setting up a bounty program for the community to find bugs in the code and to submit new junit tests. The website is developed here: https://github.com/ethereum/baboon

To see where tests are missing, integrate with https://coveralls.io, which is already being used by the go team.

@CJentzsch, anything special to consider when implementing this?

[sveneh]

@tgerring : Are you maintaining the ethereum coveralls account?

[tgerring]

@sveneh Only for the go-ethereum repo thus far. We're in the middle of some refactoring that is breaking tests, so coveralls is probably a bit out of date.

[CJentzsch]

@sveneh I already talked with @kaeptnjoda about it, so she knows the details. Basically rewarding people for :

1. submit a test to the test repo that breaks consensus
2. submit a test that prooves a bug in the client
3. adds test to increase test coverage

[kaeptnjoda]

I am assigning @Gustav-Simonsson to this issue. He's been working on setting up the bug bounty program.