#11 Support annotation at field level

[Mingfai]

Currently, the @JSON annoation works in the method level. It is desirable to be allowed to define annotation at field level.

My reasons are:
1. Java Persistence API that defines @Entity annotation also support both field and method level annotation. I suppose it is a good practice.

2. Getter/setter generation. Getter and setters are usually generated by IDE, and may be removed and recreated.

3. Code clarity. member variables are listed at the first part of a class and it's more clear to read the @JSON annoation

[Charlie Hubbard]

This was fixed long ago.