01-Signing.js - 'sign' function is taking in Buffer, might need to add 'toString('hex')'

[emelendez89]

https://github.com/hyperledger/education-cryptomoji/blob/dd3d2b38ec59471735b0e28bea37e707f53a32d4/code/part-one/tests/01-Signing.js#L69 Should take Buffer as it shown in the documentation

[delventhalz]

The use of randomBytes to create random messages for testing has caused some confusion. The simplest sign implementation will likely handle either strings or Buffers fine (because createHash handles both strings and Buffers), so I was not particularly specific about which to accept. This is clarified in a new PR (referenced below):

• part one's sign method must be able to handle strings
• part two's sign method must be able to handle Buffers