version 2.5.0

About half of these are ported from https://github.com/pusher/oauth2_proxy/ pull requests, and link to there in the PR description.

Changes:

• #26 websocket proxying support (hopefully ;)
• #17 add option --flush-interval
• #14 rename import path to github.com/ploxiln/oauth2_proxy
• #15 update vendored dependencies, and version of "dep" used in Travis-CI and Dockerfile
• #16 minor Google and OIDC options handling code cleanup

Fixes:

• #22 #24 fix option --redirect-url handling
• #19 make --ssl-insecure-skip-verify keep most DefaultTransport configuration (timeouts, keepalives, etc)

Provider updates:

• #28 actually support Google nested groups - oauth2_proxy v2.4 claimed this, but didn't
• #13 add Discord provider
• #21 OIDC provider: add option --skip-oidc-discovery
• #25 OIDC provider: fallback from "email" to "sub" (Subject)
• #23 GitHub provider: rename url query param "limit" to "per_page"