Add do_call macro, implement Bool builtins, add tests

* I noticed that `fn call(...)` in all objects was identical, so I made
  a macro for it. This should make things a little easier to read, since
  do_call is about 30 lines a pop.
* Bool has a constructor now, and a to_int and to_float implementations
* Add tests for constructors and add new bool tests

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

tests/float.npp.expect

@@ -96,3 +96,11 @@ __neg__
 -0.0
 0.0
 -0.0
+constructor
+10.0
+10000.0
+0.012
+1234.0
+1.5
+1.0
+0.0