message: ECPair: simplify `getPublicKeyBuffer`
  The BigInteger type provided `bigi` already supports padding (as seen
  a few lines below in `toWIF()`)
  The custom padding is not required.
  Issue:
diff: @@ -138,15 +138,7 @@ ECPair.prototype.getPublicKeyBuffer = function () {
  ECPair.prototype.getPrivateKeyBuffer = function () {
  if (!this.d) throw new Error('Missing private key')
  - var bigIntBuffer = this.d.toBuffer()
  - if (bigIntBuffer.length > 32) throw new Error('Private key size exceeds 32 bytes')
  -
  - if (bigIntBuffer.length === 32) {
  - return bigIntBuffer
  - }
  - var newBuffer = Buffer.alloc(32)
  - bigIntBuffer.copy(newBuffer, newBuffer.length - bigIntBuffer.length, 0, bigIntBuffer.length)
  - return newBuffer
  + return this.d.toBuffer(32)
  }
  ECPair.prototype.sign = function (hash) {
  