Automatic creation + updating of Gemfile on `fastlane init`

* Automatic creation + updating of Gemfile on `fastlane init` (#11582) via Felix Krause
* Update helper to better handle Xcode Server (#11611) via Joshua Liebowitz
* Don't override demo_account_required befor submit_for_testflight_review! (#11609) via Joshua Liebowitz
* Fix scan poster when providing a custom channel (#11612) via Felix Krause
* Update installation methods across fastlane (#11600) via Felix Krause
* Fix broken and old links (#11593) via Iulian Onofrei
* Write dSYMs in binary mode to avoid UndefinedConversion error (#11592) via Michael Smith
* Fix spec path separator (#11597) via Jan Piotrowski
* Fix for Travis CI not installing WWDRC how we expect it (#11594) via Joshua Liebowitz
* Version bump to 2.77.0 (#11613) via Joshua Liebowitz

https://github.com/fastlane/fastlane/releases/tag/2.77.0
