make function printing more demo-friendly

I found that even printing a handful of methods when showing a generic function was very disruptive while presenting using IJulia, so this pull request changes generic functions to just print a single-line summary. It also makes printing anonymous functions and intrinsics match in style. The new style can be seen in [this IJulia notebook](http://nbviewer.ipython.org/b8fe9dbb36c1427b9f22).