Summary:
Change Hash::getBytes() to return a folly::ByteRange rather than a
std::array<uint8_t, 20>. This makes Hash more convienent to use with existing
APIs that accept a ByteRange. (For instance, IOBuf.)
There were only 2 call sites using the existing getBytes() functionality,
and they only used the data() method on the returned std::array, so they don't
have to be updated at all to use a ByteRange.
Reviewed By: bolinfest
Differential Revision: D3354581
fbshipit-source-id: 8f2a3c196e59620fb5b0fb2caf4d1d7f26e1d2c4