Update documentation for crc32c, cpu
Merge pull request #119 from harshavardhana/pr_out_update_documentation_for_crc32c_cpu
Add license header
Merge pull request #120 from harshavardhana/pr_out_add_license_header
Refactor checksum code, and add Objectname hashing per uploaded objects

Add placeholder sha256, sha512 implementations from Intel with AVX, AVX2
and SSE4.1 extensions - with some boilerplate Go code.
Merge pull request #121 from harshavardhana/pr_out_refactor_checksum_code_and_add_objectname_hashing_per_uploaded_objects