Fix find_class_by_name function.

Merged #15

Improve correctness

Merged #3

Reduce crate size

Replaced resources/classes.dex with a smaller one.

Add more documentation and API changes.

• Added documentation and references to Android docs to most structs.
• Made some more parts of the library public.
• Changed Class::static_fields, Class::instance_fields, Class::direct_methods, Class::virtual_methods, Class::static_values to return empty values rather than Option

Inital release

Initial release.