k should be 32 bytes, not 8 bytes

This is a bug with security implications. It is much easier to guess the value
of k within a 64 byte range. This would lead to compromised private keys.

The cryptography interface of bitcore is extremely poor. I recommend:
* Get rid of the C++ code, since it makes everything more difficult with little benefit
* Refactor all crypto, and have easily auditable bignum, point, ecdsa, and key classes
* Then actually audit the crypto
Merge pull request #482 from ryanxcharles/bug/k-too-small

k should be 32 bytes, not 8 bytes
Add BIP21 implementation
Add validation of required arguments for future use
paypro: example - use GET method for first paypro request.
Merge pull request #484 from chjj/fix_paypro_example

paypro: example - use GET method for first paypro request.
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
version 0.1.35
Added definitions for the dogecoin networks to networks.js
Merge branch 'dogecoin_support' of https://github.com/zmanian/bitcore into dogecoin_support