Fix for Issue #12

Fixed crash where wrong ctor was sometimes called. Appears to be platform and JVM dependent. 
Crash was consistent on Linux with Java7. The problem is that the FormatOption class has 2 single param ctors. Line 92 of Book.groovy calls the modifed method with null for the name param. This then in turn calls new FormatOption(null), which on Linux/Java7 calls the FormatOption(FormatOption parent) ctor not the FormatOption(String name) ctor as apparently happens on other platforms and on Linux with Java6.