Add create - a partial polyfill for Object.create
Change environment#append to environment#envAppend
Change dispatching on operators to dispatching on names

>= becomes flatMap
>> becomes kleisli
 < becomes map
 * becomes ap
 + becomes append
Use AnyVal in tests when just checking equality
Don't set non-writable properties on Function

Specification says .length is non-writable. The .name property is
non-standard but seems to be non-writable in most implementations.
Update README