The 1.6 Launcher Has Came Out XD If You Guys Didnt Know You Can Change Your Minecraft Versions Pretty Easy Now.

Step 1. Open the new launcher

Step 2. On the right of the new launcher u should see the button "New Profile" Click It

Step 3. Once you click it you should see a new windows appear named "profile editor"

Step 4. Name it whatever you want and tick the "use game directory box" If you want to use texture packs and mods and saves for it (OPTIONAL)

Step 5. Once you named it and tick the box you should see under it "Use Version" open it and choose the version you want for example i chose 1.5.1

Step 6. Ignore The Java Advance thing and click save profile

Step 7. Once you clicked save profile the window should close

Step 8. On the top right corner of minecraft you should see profile selection and under it Profile: Click the Down arrow key and select the profile you made

Step 9. Click play button

Hope This Helps You Guys Who Wanted To Play On Your Older Version Of Minecraft