doc: add clear listener methods 

release: v0.50.0 

release: v0.30.0 

pkg: Bump minor version (v0.28.0 -> v0.29.0) See `CHANGELOG.md`.

pkg: Bump minor version (0.27.1 -> 0.28.0) 

docs: Update changelog 

v0.27.0 Added: 1. Add constructor options: * (yagop#243) `options.polling.params` (by @GochoMugo, requested-by @sidelux) 1. Add methods: * (yagop#74) *TelegramBot#removeReplyListener()* (by @githugger) 1. (yagop#283) Add proper error handling (by @GochoMugo) 1. (yagop#272) Add health-check endpoint (by @mironov) * `options.webHook.healthEndpoint` 1. (yagop#152) Add test for TelegramBot#sendDocument() using 'fileOpts' param (by @evolun) 1. Document `options.webHook.host` (by @GochoMugo) 1. (yagop#264) Add Bot API version to README (by @kamikazechaser) 1. Add examples: - (yagop#271) WebHook on Heroku (by @TheBeastOfCaerbannog) - (yagop#274) WebHook on Zeit Now (by @ferrari) Changed: 1. (yagop#147) Use *String#indexOf()*, instead of *RegExp#test()*, to find token in webhook request (by @AVVS) Fixed: * Fix bug: - (yagop#275, yagop#280) fix es6 syntax error on Node.js v4.x (by @CrazyAbdul) - (yagop#276) promise.warning from `request-promise` (by @GochoMugo, reported-by @preco21) - (yagop#281) fix handling error during polling (by @GochoMugo, reported-by @dimawebmaker) - (yagop#284) fix error during deletion of already-set webhook, during polling (by @GochoMugo, reported-by @dcparga) 1. Fix links in documentation (by @Ni2c2k)

pkg: Bump minor version 

Release v0.20.1.