Fix error messages for some illegal constructions, fix absolute path includes (#251)

* Updated tests, banned type decls and toplevel letvals

* Properly ban nested contracts

* Fix including by path

* Fix error message test

* Fix prettpr attr display. Make dialyzer happy

* More tests

* Fixed type printing

* Updated docs

test/contracts/voting.aes

@@ -1,16 +1,3 @@
-
-/* Contract type */
-contract VotingType =
-  type state
-  function init            : list(string) => state
-
-  function giveRightToVote : address => unit
-  function delegate        : address => unit
-  function vote            : int => unit
-  function winnerName      : unit => string
-  function currentTally    : unit => list(string * int)
-
-/* Contract implementation */
 contract Voting =
 
   // Types