Provide documentation of attributes in Jobs class

[jhkennedy]

Job instances have a lot of attributes that are currently undocumented:

hyp3-sdk/hyp3_sdk/jobs.py

Lines 31 to 41 in 819e790

	self.job_id = job_id
	self.job_type = job_type
	self.request_time = request_time
	self.status_code = status_code
	self.user_id = user_id
	self.name = name
	self.job_parameters = job_parameters
	self.files = files
	self.browse_images = browse_images
	self.thumbnail_images = thumbnail_images
	self.expiration_time = expiration_time

It'd be nice to provide them as a class level docstring -- see:

• Our Style Guide
• Other examples