turned get/set methods into properties and introduced read-only
properties if only get method available (less Java, more Python like);
added generic access to Java methods using javabridge's JWrapper and
JClassWrapper classes
updated examples
extended use of properties
added convenience methods `class_is_last()` and `class_is_first()` to
`weka.core.Instances` class
added convenience methods `delete_first_attribute()` and
`delete_last_attribute()` to `weka.core.Instances`
updated requirements for javabridge: 1.0.9+
updated API calls
tidied up a bit, referencing the "Installation" section now rather than duplicating the information