Fixed variable error in wpsc-shipping/usps_20.php

The variable being tested is NOT the one being assigned the new instance of ASHTools().
Need to be able to cart item image customization on shopping cart page.
Using a filter just as is done in wpsc_cart_item_url() would be
consistent.

Issue #148
Escape image links
Update readme.md

Just fixing some weird opensource stuff.
Fix 'also bought' product names and undefined margin var.
Call wpsc_populate_also_bought_list() via 'wpsc_submit_checkout' filter.
Fix SQL IN error in wpsc_populate_also_bought_list().
Tidy up wpsc_also_bought() code and reference correct 'no image' image.
Fun fact: Walk Like an Egyptian was the Number One hit song the year I was born.  For bonus points, how old does that make me?
removing usages of $wpdb where declared but never used
Add filters to allow additional columns on the sales log screen
More filters for purchase logs page
Fix documentation typo in wpsc_find_purchlog_status_name
Check that 'xmlformat' query parameter is set.
Escape enclosure URL in product feed.
Delete FPDF.
Merge pull request #178 from benhuson/origin/delete-fpdf

Delete FPDF files.
Filter gateway checkout form output
Remove name="submit" from checkout page submit buttons
Merge pull request #184 from leewillis77/submit_fix

Remove name="submit" from checkout page submit buttons