Require python >= 3.6

[sbidoul]

closes #110

[codecov-commenter]

Codecov Report

Merging #115 (5f669c5) into master (478983c) will decrease coverage by 0.61%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #115      +/-   ##
==========================================
- Coverage   93.16%   92.55%   -0.62%     
==========================================
  Files          14       14              
  Lines         892      886       -6     
  Branches      157      154       -3     
==========================================
- Hits          831      820      -11     
- Misses         43       45       +2     
- Partials       18       21       +3     

Impacted Files	Coverage Δ
click_odoo_contrib/backupdb.py	98.46% <ø> (-1.54%)	⬇️
click_odoo_contrib/copydb.py	100.00% <ø> (ø)
click_odoo_contrib/core_addons/__init__.py	100.00% <ø> (ø)
click_odoo_contrib/dropdb.py	95.83% <ø> (ø)
click_odoo_contrib/manifest.py	100.00% <ø> (ø)
click_odoo_contrib/restoredb.py	69.09% <ø> (ø)
click_odoo_contrib/_dbutils.py	100.00% <100.00%> (ø)
click_odoo_contrib/initdb.py	95.89% <100.00%> (-1.06%)	⬇️
click_odoo_contrib/update.py	85.45% <100.00%> (-1.38%)	⬇️
... and 2 more

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[sbidoul]

I'm going ahead and merging this. Previous versions will remain available on PyPI with support for Python 2 and 3.5.