Fix dailyAverages query on session update & test

- Add dailyAverages seeds
- Start implementing testing

data/migrations/01-createUsersSessionsAndDailyAveragesTables.js

@@ -52,6 +52,7 @@ exports.up = function(knex) {
 			.unsigned()
 			.notNullable()
 			.references('sessions.id')
+			.unique()
 			.onUpdate('CASCADE')
 			.onDelete('CASCADE');
 		tbl
@@ -66,7 +67,7 @@ exports.up = function(knex) {
 			.unsigned();
 		tbl
 			.float('average_mood');
-	})
+	});
 };
 
 exports.down = function(knex) {