Add coverage and basic test to smart-contracts

[garatortiz]

Closes #39

[fvictorio]

When I go to the blockchain directory and run npm test (after starting the ganache script in another terminal), I get this error:

Error: Could not find artifacts for PoBa from any sources

[garatortiz]

ummm actually, I don't know. I have run npm test, in the same directory -blockchain-, an this is the output:

[fvictorio]

I did a fresh clone of the project, moved to this branch, installed all packages, started ganache in the root and then npm run test in the blockchain directory. I'm still getting this error.

[garatortiz]

Ok... I'll do the same and try to replay it