Implementation of post meta table

[joworeiter]

Hi there, I was wondering if I could offer a Pull Request for the post meta table. But before I would like your opinion on how to implement it. In a project of mine I did a quick implementation with a trait of BaseModel Class since post_meta doest has an ID column and so it would throw ab error. Eventhough this works, I was wondering if it's not better to create a new abstract class, which contains the Id, so that there is more flexibility on creating own tables. Thanks for your feedback!

[rjjakes]

I was wondering if it's not better to create a new abstract class, which contains the Id, so that there is more flexibility on creating own tables.

I think this is a good idea @joworeiter

[joworeiter]

#9 Pull Request is here!

[rjjakes]

I've merged your PR to master