added try/except for selectors import since selectors was moved out of asyncio in python 3.4

To expand on title, selectors was moved out of asyncio in python 3.4 (see: http://docs.python.org/3.4/library/selectors.html#) so 

```from asyncio.selectors import (...)```

does not work any more, you now have to use:

```from selectors import (...)```

Adding a simple try/except ImportError fixes that.