Gateways should show if there's a total

In a case where an item has a fee but ends up being zero (e.g. discount) the user should be able to purchase.

Note: Untested and I'm assuming gateway some logic/integrations could fail.
Pass the discounts array to the filter.

Allow for filters to know as much as the function.
Add quantity to email receipts
#2583 - Do not show in/excluding tax when items are free (for cart and add to cart buttons
Remove HEAD/master merge notes.

It appears that during a merge, "<<<<<<< HEAD" and ">>>>>>> master" labels were left in the widget code. These have been removed.
Merge pull request #2641 from tollmanz/master

Remove HEAD/master merge notes.
#2583 - Moving to edd_is_free_download
Revert "Pass the discounts array to the filter."

This reverts commit a170732ff1b21d0f5d21955b193178a2f3040c79.
Merge branch 'issue/2583' of github.com:cklosowski/Easy-Digital-Downloads into cklosowski-issue/2583
Merge branch 'cklosowski-issue/2583'
Merge pull request #2636 from ghost1227/issue/2521

Add quantity to email receipts
Merge pull request #2642 from dancameron/bug/show-gateways

Show Gateways based on Cart Total
Check if price_id exists within prices
Merge pull request #2644 from elliott-stocks/patch-10

Check if price_id exists within prices