Add options

[jbblanchet]

Right now the second parameter is a list the properties to observe. I think this should instead be an option object, so we can add more features easily without breaking compatibility. Sample features that could be added are recursion (see #24), properties to exclude instead of to include, custom property filter function (for example to exclude all properties beginning by _ or $), and plenty of other way better ideas.

[archangel-irk]

It is a good idea and I'll think about how to improve it.

[unsafecode]

+1

[archangel-irk]

Since 0.2.0-alpha added options deep and fields.