Fix #101
Fix #101

Fix #'cats.core/mapseq documentation

Returns a seq not a vector.

Remove unnecessary quote in #'cats.core/mapseq

There's no need to quote the empty list.
Reference: http://clojure.org/cheatsheet
Create	() list list*

- Remove not-empty precondition.
- Similar to #'cats.core/foldm, if the given collection is empty,
  return the empty list wrapped the current monadic context.
- Update docstrings:
  - Add examples using ctx/with-context and the empty list.
  - Clean up require form
  - Use ;; => #<Monad [value]> convention

tcsavage/cats,funcool/cats,yurrriq/cats,alesguzik/cats