readme tweaks
readme tweaks

Note that Chrome requires https for voip (fixes #2506)

Remove lies about where issues are filed.

vector-im/riot-web,martindale/vector,martindale/vector,vector-im/vector-web,vector-im/riot-web,vector-im/vector-web,vector-im/vector-web,vector-im/vector-web,vector-im/vector-web,vector-im/riot-web,vector-im/riot-web,vector-im/riot-web,vector-im/riot-web