Add erasure coding and decoding using Intel Storage Acceleration library

 - move contrib/erasure --> contrib/isal
 - bring in low level 'isal' package for Go for exposing C functions
 - Implement Erasure 'encoding'
   Supports - Reed Solomon Codes, Cauchy Codes
 - Implement Erasure 'decoding'
   Supports - Reed Solomon Codes, Cauchy Codes