Add BIP21 implementation
Add validation of required arguments for future use
Skip BIP39 tests on Travis
bip21: use RegExp.exec instead of String.match.
bip21: use triple equal for consistency.
bip21: check for arg `r=` and set merchant.
Merge pull request #1 from chjj/feature/BIP21

Feature/bip21 - some changes
bip21: fix regex parse error.
Merge pull request #2 from chjj/feature/BIP21

bip21: fix regex parse error.
Merge pull request #483 from yemel/feature/BIP21

Feature/bip21