add support for a FLUTTER_DEV env var in the flutter script
add support for a FLUTTER_DEV env var in the flutter script

Hixie/flutter,turnidge/flutter,flutter/flutter,Hixie/flutter,flutter/flutter,cbracken/flutter,flutter/flutter,tvolkert/flutter,Hixie/flutter,cbracken/flutter,flutter/flutter,tvolkert/flutter,flutter/flutter,turnidge/flutter,tvolkert/flutter,tvolkert/flutter,flutter/flutter,Hixie/flutter,Hixie/flutter,cbracken/flutter,Hixie/flutter,cbracken/flutter,cbracken/flutter,cbracken/flutter,cbracken/flutter,aghassemi/flutter,cbracken/flutter,flutter/flutter,Hixie/flutter,flutter/flutter,tvolkert/flutter,cbracken/flutter,aghassemi/flutter,turnidge/flutter,tvolkert/flutter,flutter/flutter,tvolkert/flutter,aghassemi/flutter,cbracken/flutter,Hixie/flutter,turnidge/flutter,turnidge/flutter,aghassemi/flutter,tvolkert/flutter,tvolkert/flutter,Hixie/flutter,flutter/flutter,Hixie/flutter,tvolkert/flutter