MaxListenersExceededWarning fix

[devMYC]

No description provided.

[coveralls]

Coverage increased (+0.01%) to 85.88% when pulling 55b08d3 on devMYC:1.0-fix into f5809e4 on ethereum:1.0.

[frozeman]

I'm declined to merge this, as it would silently fail and not tell the developers that the subscription was not created.
Also this assumes that all providers which support .on() are event emitters with a maxListener.. function.
We should think about a way to return proper warnings in such cases so that the dapp dev can take care of cleaning up subscriptions.

[devMYC]

@frozeman yeah totally agree, definitely need a better solution to solve this problem. I'm currently just using this hack to ignore the warning when running tests.

[frozeman]

Then lets think about a real solution, Ill close this.