Skip benchmarks if /usr/share/dict/words isn't readable.
Skip benchmarks if /usr/share/dict/words isn't readable.

Fixes #1.

golang/snappy,winlinvip/snappy,FactomProject/snappy-go,monkeybutter/snappy,FactomProject/snappy-go,bmatsuo/snappy,btcsuite/snappy-go,golang/snappy