Activate dependabot

[joshmoore]

Close #732

[codecov]

Codecov Report

Merging #734 (101703c) into master (ab5d91b) will decrease coverage by 0.48%.
The diff coverage is n/a.

❗ Current head 101703c differs from pull request most recent head 458dee2. Consider uploading reports for the commit 458dee2 to get more accurate results

@@            Coverage Diff             @@
##           master     #734      +/-   ##
==========================================
- Coverage   99.92%   99.44%   -0.49%     
==========================================
  Files          28       28              
  Lines       10408    10408              
==========================================
- Hits        10400    10350      -50     
- Misses          8       58      +50     

Impacted Files	Coverage Δ
setup.py	0.00% <ø> (ø)
zarr/util.py	85.67% <0.00%> (-14.33%)	⬇️

[joshmoore]

I haven't heard any objections. Merging and if dependabot becomes annoying we can always disable.

[joshmoore]

All bumps generated from this activation are green. Merging them all which will cause all PRs to start being tested with them. If necessary, we can either rollback and/or have a more conservative version of the requirements while which also gets tested. Thoughts welcome.