Changes Driver.find() to accept an aditional initial param called fields

Changes anything that depends on Driver.find()
Adds .only() to ChainFind allowing people to filter returned parameters

Adds test for .only() too
Add .only() for hasMany() relations
Merge pull request #8 from bramus/only-for-many

Add .only() for hasMany() relations
Fixes previous commit when no conditions are defined (#8)
Changes hasMany get*() to allow chaining just like Model.find()
Adds test for hasMany get*() without callback (chaining)
Extends Readme.md Models section by giving more options and showing how to chain methods
Fixes Readme.md example not formatting as javascript
Adds Bramus Van Damme as contributor
Bumps version to 2.0.0-alpha6
Updates orm.connect and orm.use to avoid unhandled exceptions
Makes mysql and postgres drivers use config.href (original url string) if defined (fixes #9)

This will allow people to pass options directly to drivers
Adds autoFetchLimit to associations and globally (default: 2)

This avoids infinite loops when associations have these loops. By
defining a limit, for every association level fetched, the limit drops.
When it reaches zero no more associations are fetched.
Fixes Readme example, adds more examples describing autoFetch
Reorders One/Many association options
Adds reverse option to hasOne associations allowing to fetch instances from the association model

Example:
A.hasOne("b", B, { reverse: "parentA" });

Creates:
A.getB() **and** B.getParentA();
Fixes mysql escape (fixes #10)
Forces INSERT when creating instances using `new Model()`, even if it has an ID (#11)
Adding the ability to define a comparison opperator for comditions along
with a unit test.