Expand angular tests

[pimotte]

The tests run by ng test are marginal. These should probably be expanded. I have tried to work on this, but I was running into some issues with the styles of import we're using for the truffle-contract.

[pimotte]

Tests on Web3Service have been added. A MetaCoinService should probably be extracted from the MetaCoin sender, at which point both the component and the service can be tested.