USER STORY: Add size and colour models to Products app.

[johnamdickson]

Epic: Products Set Up and Interactions #9

User Story: As a user I can browse available item sizes and/or colours so that I can make an informed decision on product sizing and preferred colours.

Acceptance Criteria:

• A size and colour model in the products app.
• A representation of size and colour availability on the product detail page.
• A size chart for the user.

Tasks:

• [x] Add models for size and colours with respective addition to admin and views files.
• [x] Confirm data is being returned to template.
• [x] Create a means of displaying available sizes and colours in the product detail page.
• [x] Link size chart to open in new tab.

[johnamdickson]

Size and colours models created and linked back to template via usual route. Available sizes and colours detailed on product detail page. Size chart added as link in sizes pop up which opens in a new tab.