Better display for default props those are functions

[ritz078]

Currently it shows as

Issues:

• Formatting and Highlighting not present
• Displayed code should be ES2015

[roonyh]

Displaying default values is improved in #16 for functions and some other stuff as well. For functions only the function name is displayed. Function body is not shown at all. What do you think?

#16 is in v3.0.7

[ritz078]

I understand its tough to show the whole function that too in ES2015. But just a function is incomplete information. It won't help the user anyway until that function is documented anywhere.