Add Read/Write Connections and Fix SQLite Connections

[MitchellMcKenna]

• Add compatibility support for Database Read/Write Connections which was added in Laravel 4.1 (changelog).
• If db config specifies read/write params a Doctrine MasterSlaveConnection will be created instead.
• Fix SQLite not being able to connect, as laravel db setting database must change to path for doctrine.
• Fix ignoring port config param not allowing user's to specify a custom mysql port.

Implementation notes: I tried to mimic the same way Laravel detects a Read/Write Connection:

• Checking if Laravel's read/write connection is turned on is done by looking for 'read' param, the same as in Laravel's code here.
• Getting $writeConfig and $readConfig is done the same as in Laravel's code here.

[MitchellMcKenna]

@mitchellvanw I've updated this pull request with the changes from #10 being merged into master. This will also fix SQLite not currently working in master.

[pintomau]

Yes please.

[mitchellvanw]

@MitchellMcKenna this is really useful and will be added. The only problem is that I'll be merging in Kirk's new database config PR #31 and that will make it so that I can't merge this in. Thanks a lot for the suggestion!