fix build error caused by rust recent change: purely namespaced enums
fix a build error: num.abs
fix a build error caused by that the Zero trait is no longer implemented for Duration
fix failed test
Merge pull request #32 from windor/build-error-fixed

fix build errors caused by purely namespaced enums and druation api changes
Refs None, proc() -> move ||
Rename crate name from zmq(taken) to zeromq, and update for cargo.
Fix README renaming
Use tuple indexing
Implement Copy for enums