Add `cargo build` to .travis
Add `cargo build` to .travis

serde-rs/serde,jmesmon/serde,Hoverbear/serde,sidred10/serde,JohnHeitmann/serde,Byron/serde,Ticki/serde,3Hren/serde,erickt/serde,oli-obk/rust-serde,thorbenk/serde,infinityb/serde,pcwalton/serde,csmulhern/serde,tempbottle/serde,eefriedman/serde,skade/serde