NSCalendar extension Undocumented

[valery-bashkatov]

I have extension for the NSCalendar, but Jazzy doesn't document its description.
Jazzy 0.6.2

Example:
`import Foundation

/// NSCalendar extension for testing Jazzy
public extension NSCalendar {
public var test: Double {
return 1
}
}`

And the documentation looks like this:

[jpsim]

Looks like a duplicate of #454. I have a fix for that in the works.