I have found a way to get the 1.7.2 version folder back. This will allow you to mod Minecraft 1.7.2. If this has already been found, then I am sorry about this and I will feel stupid. Here are the steps to mod 1.7.2!
1: Run Minecraft 1.7.2
There should already be a profile created for it
2: Generate a world
3: Exit MC
4: Go to %appdata%>Roaming>Minecraft>Versions>1.7.2
6: Cry when you open Minecraft the next time and see your modded folder erased and replaced with a fresh one. To install mods after 1.6, you actually need to do a little more than that.
5: Make a copy of the 1.7.2 folder and name it something else (In this example we'll call it "1.7.2 - Mods", but you can call it whatever you want. Use the chosen name instead, anywhere that I use "1.7.2 - Mods".)
6: In the copied folder, rename 1.7.2.jar to 1.7.2 - Mods.jar
7: Rename 1.7.2.json to 1.7.2 - Mods.json
8: With a text editor, edit "1.7.2 - Mods.json" and change the line "id": "1.7.2", to "id": "1.7.2 - Mods",
9: ...now you can start modding the "1.7.2 - Mods.jar" file.
Village Mechanics: A not-so-brief guide - Update for 1.4! Added subsection on iron farming to the iron golems section. Only ten villagers required to spawn golems (down from sixteen)! Put to rest the "facing doors cancel each other" myth!