Allow puncutation in class names

[jgreywolf]

          I don't know how you folks see this. I feel like not allowing punctuation in a class name is a show stopper.

What can I do about it?

Originally posted by @michimussato in #1546 (comment)

[jgreywolf]

From: @michimussato
Getting there, but still not quite...
Introduced some unexpected behavior:

classDiagram
    class my.module.MyClass {
        __init__(self)
        __hash__(self)
    }

results in:

[jgreywolf]

From @michimussato

Apparently, backticking the class name gives me the desired result:

[...]
class `some.modules.Class` {
   processNestedSchemas(self) 
}
[...]
node10  -->  `some.modules.Class`
`some.modules.Class`  -->  node9 
`some.modules.Class`  -->  node3 
node10  -->  node7 
`some.modules.Class`  -->  node8