add tests for the bit operations

far too extensive, but a good demonstration of the base 2 literal
syntax...
add bit-not
add array tests
add ns-map to get the names & vars of a namespace

it doesn't go through the refers yet, but i'm not sure if we want that.
add when-not
implement refer as in clojure

the previous refer is now `refer-ns`. i'm not sure if i should have used
the Refer class, but that would have required more code in rpython, i
think.

theoretically we could now use this to replace `include_stdlib` with a
call to `(refer 'pixie.stdlib :refer :all)`.
Merge pull request #40 from heyLu/bitops-and-arrays

Bitops and arrays tests
Merge pull request #42 from heyLu/namespace-improvements

Namespace improvements
Merge branch 'master' into async-io
some fixes and the like