trim newlines in ERB closing tags

The robots.txt spec doesn't mention newlines at the top of the file but given the importance to robots.txt to ecommerce sites, I'd rather be safe about keeping a clean file.

This is a simple instruction to the ERB constructor to eat newlines on lines ending with %> primarily so I don't have a newline at the top of my robots.txt

http://ruby-doc.org/stdlib-2.1.2/libdoc/erb/rdoc/ERB.html#method-c-new