Adds tests to ensure that all pre-1.0 package versions are locked

Let me know if the tests should be more thorough. I'm not checking for ranges, just for the use of `^` or `~`, but that seems to be how we specify all dependencies in ember-cli.
@rwjblue `semver` won't tell you if something like `^0.2.1` is fixed or not, which is what I'm trying to validate. It can only take a fixed version number and check if it matches a range or another version from what I can tell. I'll check again though. I could be missing something. We do want to allow `0.2.1`, just not `^0.2.1` or `~0.2.1`.