model attributes and new

Ruby Bootcamp D2: Basic Document

* instantiate a model with attributes
* read, write attribute
* get all attributes
* a mock `new_record?` method
declare fields

Ruby Bootcamp D2: Basic Document

* add `field` Class Macro to Model. This will do:
  * add getter & setter methods for attribute
  * add a `Mongoid::Field` object to the maintained `fields` Hash
  * check duplicate field before adding object
mass-assignment & initialize

Ruby Bootcamp D2: Basic Document

* mass-assignment with `Model#process_attributes` method
* `process_attributes` is used by `Model#initialize`
declare field aliases

Ruby Bootcamp D2: Basic document

* accept options in `field` method
* use options[:as] as an alias. Add alias methods
setup rspec
setup travisCI