Extra argument for price option amount filter

Price id should also be passed to this filter
Extra arg to edd_complete_download_purchase filter

This is addition to Software Licenses plugin so it can save order of
each download item in the cart
Merge pull request #2775 from somewebmedia/Enhancement/filter-price-amount

Extra argument for price option amount filter
Changed $cart_order to $cart_index
Merge pull request #2776 from somewebmedia/enhacement/download-cart-order

Extra arg to edd_complete_download_purchase filter
Scrutinizer for code coverage
Update .scrutinizer.yml
Update .travis.yml
Update .travis.yml
Swap to use Scrutinizer for code coverage
Remove backticks from CREATE TABLE SQL.

These are not supported by dbDelta and cause a Notice. Fixes #2781.
Merge pull request #2782 from jjeaton/create-table-notice

Remove backticks from CREATE TABLE SQL.
change default item count in [downloads] shortcode from 10 to 9 - #2785
Merge pull request #2786 from sdavis2702/master

change default item count in [downloads] shortcode from 10 to 9 - #2785
Make sure discount code exists before trying to apply it

Checks that the discount code exists before trying to apply it, otherwise `edd_get_discounted_amount()` will return `0`.

When this is then subtracted from `$price` and inverted to make `$discounted_price` here:

`$discounted_price -= $price - edd_get_discounted_amount( $discount, $price );`

 it'll always equal the negative value of the price giving the user a 100% discount.
Merge pull request #2791 from lukechilds/patch-2

Make sure discount code exists before trying to apply it
Add onChange event for CC validation #2801
Fix some coupon insert hooks + prevent notices
Merge branch 'JeroenSormani-master'
Merge pull request #2802 from juanfraa/master

Add onChange event for CC validation #2801