Merge tag 'v1.1.5'

1.1.5

 * Update README.md (Rand McKinney)

 * Add contribution guidelines (Ryan Graham)
Map required/id properties to NOT NULL

See https://github.com/strongloop/strong-arc/issues/600
Merge pull request #15 from strongloop/feature/fix-arc-600

Map required/id properties to NOT NULL
Update deps
v1.1.6
Merge branch 'release/1.1.6' into production