Add isatty() to FakeStdin.
Add isatty() to FakeStdin.

This closes issue #28.

hirochachacha/apython,wevial/bpython,kdart/bpython,thomasballinger/old-bpython-with-hy-support,aktorion/bpython,kdart/bpython,aktorion/bpython,myint-archive/bpython,wevial/bpython