Adding minor fix to $save method when pk is also null

Merge pull request #28 from letanure/master

Prevent bower install warns

Added some cool options for calls that allows you to change the call …

…type such as model.({name:'Klederson'}, {url: http://myCustomUrl.for.this.call, method: POST}); In this way you can even use non standard API ( non RESTFull for example

Fixed #12 and added 2 new methods: and