v0.3.2

1. Fix IO#open, return a io obj if no block given
2. Fix Thread methods
3. Beam handle Exception instead StandardError
4. Wrap Socket#accept_nonblock
5. IO.select support #to_io implicit conversion
6. Add Thread::ConditionVariable
7. Fix IO#select, make sure it can return correct fds immediately

Version 0.3.2 can work with Sinatra and Puma.

See example, how to manually monkey patch on Sinatra and Puma: https://github.com/jjyr/lightio_benchmark/blob/master/server.rb