Use a 10.7 deployment target on OSX
Use a 10.7 deployment target on OSX

cc #24, although not entirely sure this will close it

rust-lang/rustup,Boddlnagg/rustup.rs,polonez/rustup.rs,nodakai/rustup.rs,Boddlnagg/rustup.rs,inejge/rustup.rs,inejge/rustup.rs,nodakai/rustup.rs,polonez/rustup.rs,inejge/rustup.rs,polonez/rustup.rs,theindigamer/rustup.rs,nodakai/rustup.rs,theindigamer/rustup.rs,rust-lang/rustup,theindigamer/rustup.rs,inejge/rustup.rs,Boddlnagg/rustup.rs,nodakai/rustup.rs,Boddlnagg/rustup.rs,rust-lang/rustup,theindigamer/rustup.rs,nodakai/rustup.rs,rust-lang/rustup,rust-lang/rustup,Boddlnagg/rustup.rs,inejge/rustup.rs,polonez/rustup.rs,polonez/rustup.rs,theindigamer/rustup.rs