Fix feature detection bug for setupPreprocessorRegistry.

[rwjblue]

The logic here was incorrect for beta versions of ember-cli (due to bizarreness in how semver package deals with prereleases).

This fixes the issue.

[Turbo87]

@rwjblue the issue here was actually that I moved from the deprecated version checker functions to using checker.for('ember-cli', 'npm'), which behaves differently. To be precise the NPM-based checker includes the prerelease stuff, while the deprecated CLI checker doesn't (see https://github.com/ember-cli/ember-cli-version-checker/blob/master/src/ember-cli-dependency-version-checker.js#L12-L13)