fix ivar warning

fixes #3108
Update OpenSSL check for new Net::HTTP::Persistent
clean up UI#trace method
make verbose GET requests easier to read
Print all HTTP responses to verbose output
Trace HTTP errors in verbose mode
Memoize slow call to #expand_path

Fixes #3104
mild Fetcher#initialize cleanup
Create persistent connection on Fetcher init.

(Might fix HTTPS request bug #3107).
Require OpenSSL instead of relying on autoload.

Apparently just letting Net::HTTP::Persistent try to autoload OpenSSL
doesn’t actually get it loaded on every machine, and then HTTPS requests
start to fail.

Fixes #3107.
Version 1.6.5 with changelog.
Merge tag 'v1.6.5'

Version 1.6.5

Conflicts:
	CHANGELOG.md
	lib/bundler/fetcher.rb