Merge pull request #27 from PatrickDropbox/master

update contributors list + add module docstring for bitvector
Don't reuse `err` declaration accross goroutines.
Use an empty struct instead of bool as map value for set.
Merge pull request #29 from aybabtme/race-on-err-assignment

[net2] Race on err assignment in test suite
Merge pull request #30 from aybabtme/set-of-empty-struct

[container/set] Use an empty struct instead of bool as map value for set.
add contributor