Small fix to Dialer to set the ServerName in tls.Config if it is empt…

…y. (segmentio#152)

Updated discardN to return errShortRead if N bytes not available (seg…

…mentio#143)

Merge pull request segmentio#121 from segmentio/clarify_special_offsets

Use named constants for special offsets

Merge pull request segmentio#106 from segmentio/compression-snappy

Add compression