RegexSet doesn't respect the ^ anchor

[kalekseev]

Compiled with regex 0.2.1

    println!("{:?}", RegexSet::new(&[r"^rooted$"]).unwrap().matches("notrooted"));
    println!("{:?}", RegexSet::new(&[r"^rooted$", r".log$"]).unwrap().matches("notrooted"));
    println!("{:?}", RegexSet::new(&[r"^rooted$", r"\.log$"]).unwrap().matches("notrooted"));
    println!("{:?}", RegexSet::new(&[r"^rooted$", r"\.log$"]).unwrap().matches("notrootedend"));

Output:

SetMatches { matched_any: false, matches: [false] }
SetMatches { matched_any: false, matches: [false, false] }
SetMatches { matched_any: true, matches: [true, false] } 
SetMatches { matched_any: false, matches: [false, false] }

[BurntSushi]

This is a literal optimization bug.