Remove explicit xcode version, let travis use default
Remove explicit xcode version, let travis use default

ghewgill/neon-lang,gitlarryf/neon-lang,gitlarryf/neon-lang,ghewgill/neon-lang,gitlarryf/neon-lang,gitlarryf/neon-lang,gitlarryf/neon-lang,gitlarryf/neon-lang,ghewgill/neon-lang,ghewgill/neon-lang,ghewgill/neon-lang,gitlarryf/neon-lang,ghewgill/neon-lang,gitlarryf/neon-lang,ghewgill/neon-lang,ghewgill/neon-lang,gitlarryf/neon-lang,gitlarryf/neon-lang,ghewgill/neon-lang,ghewgill/neon-lang