Switch to contents.add instead of add_variant

add_variant deprecated in spree v2
Add missing parameter for shipment (nil)
Add price argument
Fixes weird patch in override file. Fixes #8
No need to override spree's original find_line_item_by_variant

By overriding the original method we are no longer allowed to
remove a product (option) for the order from the backend, cause
an option's line_item will always have parent, so the OrderContents#remove
method won't find the line_item.
Revert "No need to override spree's original find_line_item_by_variant"

This reverts commit b2e16aa0edb21e3ef36e866a848a33d11c78751c.
Update line_item partial for latest spree changes

Basically just re-indented the whole block within the new
`fields_for` block, aside from applying recent changes to
the original view that were preventing adding an item 
to the cart
Set quantity default value to 1

This change was made here: https://github.com/spree/spree/commit/2717e7574d2c230ec113b5f4b19db0bc4f96f1cf

(seems like) they're assuming a value, so we better go with the flow here.
adding stock state notice on option value display
adding stock state notice on option value display
fix id targetting for propper stock location
fix type error on attribute id name
Merge branch 'fix' into 2-0-stable

* fix:
  fix type error on attribute id name
  fix id targetting for propper stock location
  adding stock state notice on option value display

Conflicts:
	app/models/spree/variant_decorator.rb
	app/views/spree/products/_options_display.html.erb
Skip adding child items if there was a error adding parent

i.e. out of stock and doesn't allow backorder
moved generator to see if it's working now
moved generators folder so not in rails folder
moved install_generator to install folder
add auto migrations option.  move engine info to engine.rb
change capital from to lowercase. changed engine name to spree_option_is_product to match name in migrations
Merge commit '2dc3dd67fcb93b0e9c74455577e54824d7bdb018'