Clear connection cache harder when entering parallel subprocesses.

Fixes #600
Modify unused opts to args
80-col
Changelog re #1026, fixes #1026
support link-local IPv6 host addresses
Changelog re #1059, fixes #1059
fix UnicodeEncodeError when fabric.api.abort/warn/puts

fix UnicodeEncodeError when fabric.api.warn

fix UnicodeEncodeError when fabric.api.puts
Refactor encoding logic
Changelog, fixes #1096
80-col
Correctly-failing version of contributed test re #1116
Applied fix re #1116 / re #852
Changelog re #852, closes #852, closes #858, closes #1116