Please loosen tether dependency

[bj00rn]

Is your feature request related to a problem? Please describe.
pinned tether dependency causes problems with multiple tether versions being installed.
as of deffde8

the issue has since been resolved in tether as of 1.4.7

Describe the solution you'd like
loosen tether dependency to ^1.4.7

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

@dominicrobertsc @reedr3 @a-b @jdgonzaleza