Escape unprintables

Hey, 

i noticed that some objects are rendered unescaped if the objects are unprintable. Printing Objects resulted in an unescaped output: `#<CLASS #x3020027F091D>`, but the output should better be `#&lt;CLASS #x3020027F091D&gt;`

I also added a method for printing symbols. The leads to an uppercased representation of the symbol.

This patch adds also two simple tests for the above cases. 

Greetings