ensure that byte code is java 1.6 compatible
ensure that byte code is java 1.6 compatible

Base64.java could have been compiled as java 1.7 byte code.

closes #32

beritou/scalaj-http,Wanderfalke/scalaj-http,scalaj/scalaj-http,OElesin/scalaj-http,OElesin/scalaj-http,beritou/scalaj-http,Wanderfalke/scalaj-http