documentation for builtins
relates #18
defclass clarification
foreach - else clarification
removed setf
Fix yielding to not suck (#151)

 This adds a class to avoid returning when we have a Yieldable
 expression contained in the body of the function. This breaks Python
 2.x, and ought to break Python 3.x, but doesn't.

 We need this fo' context managers, etc.

 This commit also has work from @rwtolbert adding new testcases and
 fixes for yielded entries behind a while / for.
Removes link to interactive demo from docs
Fix missing docstrings from defclass issue #248

Added ability to parse doc strings set in defclass declarations,
likei:

(defclass Foo [object]
  "this is the doc string"
  [[x 1]])
clarified foreach - else
Merge branch 'master' into pr/237
Merge branch 'master' into pr/251
Merge branch 'master' into pr/252
Merge pull request #243 from paultag/paultag/bugfix/fix-yield

Fix yielding to not suck (#151)

yay team