Add a memory leak testing script

I've been manually running this as:

    RUBY_HEAP_SLOTS_GROWTH_FACTOR=1 RUBY_HEAP_MIN_SLOTS=1 RUBY_HEAP_SLOTS_INCREMENT=10 RUBY_HEAP_SLOTS_GROWTH_FACTOR=.1 ITERATIONS=75000 rspec -I lib -I profile profile/memory_leaks.rb

The ruby GC settings are that way to try and make ruby increase memory really
slowly, so that we can get more accurate info on what's going on.

ITERATIONS can be whatever, but I've been running it with a really large number
so that I can be more comfortable with the results.
Fix form object memory leak

Make sure to free the first form entry with curl_formfree
http://curl.haxx.se/libcurl/c/curl_formadd.html

fixes typhoeus/ethon#43
After calling curl_easy_escape call curl_free

I think this all could also be simply replaced with CGI.escape, but we can
change that later.

fixes typhoeus/ethon#44