function RuleContext( id, severity, api, options ) {
	setReadOnly( this, 'id', id );
	setReadOnly( this, 'severity', severity );
	setReadOnly( this, 'api', api );
	setReadOnly( this, 'meta', api.meta );
	setReadOnly( this, 'options', options );
	return this;
}
Creates a rule context object.

@private
@param {string} id - rule id
@param {string} severity - rule severity (`error` or `warn`)
@param {Object} api - lint API object
@param {Array} options - rule options
@returns {RuleContext} context for rule with the given id