The way I was outputting the pubkeys would be incorrect if the first byte of
one of the coordinates was 0, since it would print the first non-zero byte
first. The solution was to use the standard openssl function that outputs a
public key to oct.
BIP32 needs to be able to add two points on the secp256k1 curve. This
functionality was not already being exposed from OpenSSL in bitcore. I have
added an "addUncompressed" function to the Key class which takes in two points
in uncompressed form, adds them, and returns the result. This is necessary for
BIP32.