change watch target to compile when product code is modified
refactor code commonalize method to check arguments

index#node and relation method should check arguments to create new object.
but this algolizme should be commonalized, and done.
refs #6 add Model#create method. To create new Object.

* Model#create is Promise based method
* Model#create call Node|Relationship#save with new Node|Relationship object
schema path should be nullable in default
refs #6 add Model#update method. To update object properties.

* Model#update is Promise based method
* it has 2 feature. to validate properties, to post request to update.
add features section