Fix [download_discounts] invalid argument warning.

An invalid argument supplied warning is thrown when there are no
discounts.
Fix empty [download_discounts] invalid argument warning.
Added missing textdomain
Add filter for $templates_dir variable

Added a simple filter (`edd_templates_dir`) to give themes the option of setting their own template directory.
Add fallback for item_number
Add Billing Details to top of billing fields
Fix typo
Fix problem with cart fees over writing cart items in PayPal
Helper function to get template directory name.
Moving edd_get_theme_template_dir_name() to template-functions.php
Added edd_get_theme_template_dir_name() function
Allow tax rates to be country-wide. #1260
Merge branch 'master' of github.com:easydigitaldownloads/Easy-Digital-Downloads
added two new actions to checkout template
Merge pull request #1255 from Studio164a/master

Add a filter for the templates directory.
Merge pull request #1254 from sumobi/master

Change "Purchase" to "Download" on Free Purchases
Hide tax billing fields if purchase total is 0.00. Closes #1252
Only add edd_before/after_download_content actions on singular download post type. Closes #1148
Fixed missing tax display
Updated version number and changelog