[PTFM-7525] Updates to support HTTPS proxies: vendor requests 0.14.2 and urllib3 1.5+dev with it. This change incorporates commit 63f58e72b7ff6f3998c86b61916c21a49a34f221 from https://github.com/kislyuk/urllib3, forked for archival from https://github.com/schlamar/urllib3, forked from canonical upstream, https://github.com/shazow/urllib3. See https://github.com/shazow/urllib3/pull/170.