VERSION 0.7.0: fix two bugs reported on GitHub, public binaries now in the wild!

Version 0.7.0 commemorates public beta binaries now being in the wild for Mac
and Linux platforms, though this actually happened a few days ago with 0.6.14.

This version fixes two bugs. First, the Linux installer/updater now supports
both systemd and regular SysV init. It will detect which your distro uses at
install/update time and install the zerotier-one service accordingly.

Secondly, this fixes an issue that caused the service to always show ONLINE
in the GUI or 'zerotier-cli info' even if there was no net connection. The
online status should be more reliably reported now.