CI doesn't check configuration w/o size_classes

[RReverser]

As mentioned in #68, but for tracking separately:

size_classes is enabled by default, so one of the lines had to remain cargo check --release but another is supposed to be cargo check --release --no-default-features to test without size_classes enabled.

Hmm, looks like there is a bunch of other places in build.sh, check.sh, appveyor.yml that use --features size_classes.

@fitzgen Does this mean they are all similarly broken (testing same configuration as default) or am I missing some switch?