tests: drop Go 1.3.3 from Travis testing
tests: drop Go 1.3.3 from Travis testing

Does not support testing.M, which means we cannot run the
test suite, which means we cannot claim to support it at
all.

rfjakob/gocryptfs,davesteele/gocryptfs,davesteele/gocryptfs,davesteele/gocryptfs,rfjakob/gocryptfs,rfjakob/gocryptfs,rfjakob/gocryptfs