[WIP] support dispatch block/data/io objects

[flier]

most of block/data/io methods can works, still need integrate with Queue with block

[flier]

hi @SSheldon and @kvark,

I'm working on a PR for dispatch block/data/io, but the iOS test case always failed, it could load other crates but can't find log, could you help to check it? Do I need change the test tool itself?

Thanks

   Compiling log v0.4.5
   Compiling rand v0.5.5
   Compiling aho-corasick v0.6.8
   Compiling dispatch v0.1.3 (file:///Users/travis/build/SSheldon/rust-dispatch)
   Compiling tempfile v3.0.3
   Compiling thread_local v0.3.6
   Compiling env_logger v0.5.13
   Compiling pretty_env_logger v0.2.4
   Compiling tests-ios v0.0.0 (file:///Users/travis/build/SSheldon/rust-dispatch/tests-ios)
error[E0463]: can't find crate for `log`
 --> lib.rs:2:1
  |
2 | extern crate log;
  | ^^^^^^^^^^^^^^^^^ can't find crate
error: aborting due to previous error