Added cookie support to HTTP::Tiny

I added cookie jar support to HTTP::Tiny.

It will work with any jar object that supports the "add" and "cookie_header" method.

I update the 001_api.t test script to account for the new "cookie_jar" attribute.

I added the 070_cookie_jar.t test script to test the validation of the jar object.

I added the 160_cookies.t test script to actually test the cookie jar in action.

The 070 and 160 test scripts use the t::SimpleCookieJar object for testing, since I figured HTTP::CookieJar might not be available.  t::SimpleCookieJar will store and return a cookie string for a given URL, but not much else.