Fixes #26 select initiator

Moving ffi_lib calls to curl.rb causes ethon to fail on Windows (Ruby
1.9.3, 2.0.0 and 2.0.0 x64). Moving it back corrects this. It may not be
pretty, but it works.
Merge pull request #47 from derikolsson/fix-select-windows

Fixes #26: Attach 'select'