I need a summary of George Orwell's Animal Farm.

Old Major, a boar, gathers the animals together after a dream he had.  He tells the animals that they need to work towards freedom from their human oppressors. He says things like, humans are the only animals that produce nothing.  He also teaches them a song - "Beasts of England."

The animals receive Old Major’s vision with great enthusiasm, but Old Major dies in chapter two. Afterwards Snowball, Napoleon, and Squealer formulate his main ideas...

Old Major, a boar, gathers the animals together after a dream he had.  He tells the animals that they need to work towards freedom from their human oppressors. He says things like, humans are the only animals that produce nothing.  He also teaches them a song - "Beasts of England."

The animals receive Old Major’s vision with great enthusiasm, but Old Major dies in chapter two. Afterwards Snowball, Napoleon, and Squealer formulate his main ideas into a philosophy called Animalism.

Animals such as Boxer are devoted. For example, Boxer's motto is “I will work harder.” Things seems perfect, until there is conflict between Snowball and Napoleon. Snowball is ousted and Napoleon takes over, and he becomes more tyrannically and belies the principles of animalism. The most egregious action is when Boxer is sold off to be slaughtered when he can no longer work. 

Finally, Napoleon changes the name of the farm back to Manor Farm, and the principles of animalism are reduced to one statement: "all animals are equal, but some animals are more equal than others."

By this time, the pigs morph into humans.