Supports merging logger stream options

This PR adds the ability to merge logger stream options to the default logger. For example:

```
var logfactory = require('appc-logger');

var logger = logfactory.createLogger({
	name: 'test-logger',
	streams: [
		{
			level: 'error',
			stream: process.stderr
		},
		{
			level: 'trace',
			path: './test.log',
			type: 'file'
		}
	]
});
```

A test case was added to `test/logger.js`