v0.3.0

• Update dev/peerDependencies (should be no breaking changes, but bumping minor version to be safe)
• Add setHasOne functionality (based on #12) and add tests
• Fix tests where assert.equal was used with incorrectly ordered parameters
• Use Promise.method to clean up a few parts and more clearly delineate which functions return promises vs. which are synchronous
• Closes #10