Merge tag 'sparks-1.2.3' into develop

1.2.3
Add a `clear_osx_cache` command, which is just a subset of what it seems to be, but helps in situations where `opendirectoryd` takes 100% of my CPU on my MBPr (all references included in comments).
minor simplification.
Major bugfix/feature: the `fabfile` should work even if local/remote are different OS type (eg. OSX to Linux, or Linux to OSX). Previously the targets worked because I used them either on same system types, or via `-H localhost`. This feature needed a consequent rewrite to be able to automatically fetch remote information *after* `Fabric` is initialized, and to avoid fetching them for every task when they are nested.
Merge branch 'release/1.3'