Allow whitespace after ( and before //

[wilkinsona]

When using Asciidoctor callouts, I'd like to be able to have a space after a ( and before a //:

RestAssured.given(this.spec).filter(document("headers", requestHeaders( // <1>

This fails at the moment with the message '(' is followed by whitespace. [ParenPad]. The following fixes it:

RestAssured.given(this.spec).filter(document("headers", requestHeaders(// <1>

Removing the space between ( and // has a detrimental affect on the HTML rendering of the callout so I'd like to be able to keep it.