v2.0.0

Breaking Changes:

• CrudService: all callback functions return promises. Callbacks are optional.
• CrudService._find no longer returns a query. use CrudService._buildQuery instead.
• CrudService._createWithRetry signature has changed (is no longer recursive)
• CrudService._update no longer returns the isModified flag
• CrudService._delete no longer returns the isModified flag

Additional Changes:

• Updated dependencies to latest versions (Mongoose 4 -> 5)
• Removed Yarn
• Updated eslint config
• Updated travis testing environments
• Updated package release files
• Mongoose.set('useCreateIndex', true); is done automatically
• Mongo useNewUrlParser: true is done automatically