This commit implements our own version of the `is-elevated` module. The
reason behind this is that `is-elevated` relies on lots of unnecessary
modules, that eventually require `spawn-sync` and `try-thread-sleep`,
which conditionally require dependencies that are not even declared in
their `package.json`, causing issues when concatenating the Etcher CLI.
See: https://github.com/resin-io/etcher/pull/1235
See: https://github.com/resin-io/etcher/pull/1228
Signed-off-by: Juan Cruz Viotti <jviotti@openmailbox.org>
