function getNodeAsString( node ) {
	switch ( node.type ) {
		case 'BinaryExpression':
			return getNodeAsString( node.left ) + getNodeAsString( node.right );

		case 'StringLiteral':
			return node.value;

		default:
			return '';
	}
}
Given an argument node (or recursed node), attempts to return a string
represenation of that node's value.

@param {Object} node AST node.

@returns {string} String value.