Refactored code that has no duplication and is less complex (GPA +1)

• refactor(Model): Split up the model class to help get rid of complexity
• fix(undefined): Promise
• refactor(jshintrc): Remove explicit use strict calls
• refactor(association): associateModel helpers
• refactor(duplication): Removed duplication of common code
• refactor(model): Extend further abstracted
• refactor(extend): Made Model.extend() far less complex
• refactor(utils): removing complexity in bootstrapEnv util
• refactor(utils): Removing complexity in bootstrapEnv util
• refactor(Model): Extend even less complex again
• fix(default): Options reverted
• refactor(Model): Removed duplicated code
• refactor(Model): Looking good
• Refactor(codeclimate): Removing complexity, duplicated code and related issues
• fix(options): Defaults are now correct
• fix(criteria): Removed old reference to where instead of criteria
• chore(docs): Contributing guide update
• release(1.2.1): Refactored code that has no duplication and is less complex (GPA +1)