fix some unit test failures (test changes only)
fix some unit test failures (test changes only)

* test_fetch_file_nonexistent used the wrong file: format - only two
forward-slashes when it should be three
* test_request_cookies_many updated to expect cookies in any order (Ruby
1.8.7 orders them differently, and it shouldn't matter)
* test_response_cookies_many updated to expect cookies in any order
(Ruby 1.8.7 orders them differently, and it shouldn't matter)
* test_response_read_file updated to work around the inability (in Ruby
1.8.7) to set the write-mode of the tempfile to binary; includes
explanation of the workaround in a comment.

sparklemotion/mechanize,gchan/mechanize,sjchakrav/mechanize,eligoenergy/mechanize,bugmelody/mechanize,uksa/mechanize,jeremiahmarks/mechanize,pwnall/mechanize,jeremiahmarks/mechanize,uksa/mechanize,pwnall/mechanize,sparklemotion/mechanize,bugmelody/mechanize,flavorjones/mechanize,eligoenergy/mechanize,sjchakrav/mechanize,gchan/mechanize