Pebble Tool v4.0-rc6

Since v4.0-rc5:

• Added the active SDK version to the output of pebble --version
• Fixed spurious update notifications for versions older than the current one.
• Resolved potential python package versioning conflicts for pypkjs
• Added a mention of subcommand help to the output of pebble --help

Pebble Tool v4.0-rc5

Bug fixes:

• pebble wipe was broken in all previous 4.0 RCs; it's fixed now.
• Environment variables are once again passed through to pebble build and friends.
• TERM not being set no longer fails builds.
• Update checks are now performed only once per day.
• Stopped displaying "b, e, t, a" instead of "beta" when the beta channel is enabled.
• Improved --tintin's handling of virtualenvs.