add codecov, tweak some spelling

[bollwyvl]

A follow-up to #379 (review), this uploads coverage to codecov, which is slightly simpler to set up, and doesn't require a secret token.

Also fixes a few spelling issues, just so we can see all the ✔️ .

[bollwyvl]

I think to get the report to show up in the issue, one button must be pushed, once, in the codecov app.

[coveralls]

Coverage remained the same at 99.729% when pulling 9ea3645 on bollwyvl:add-codecov into 0aa4cc5 on pydoit:master.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@0aa4cc5). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #384   +/-   ##
=========================================
  Coverage          ?   99.72%           
=========================================
  Files             ?       65           
  Lines             ?     8828           
  Branches          ?        0           
=========================================
  Hits              ?     8804           
  Misses            ?       24           
  Partials          ?        0           

---

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[bollwyvl]

Adding the codecov badge does require a (non-secret) token... the markdown/rst can be copied from the settings page on codecov.

[schettino72]

  .. image:: https://codecov.io/gh/pydoit/doit/branch/master/graph/badge.svg?token=wxKa1h11zn
  :target: https://codecov.io/gh/pydoit/doit

[schettino72]

When I click on "continue to full report" [1], it says the page is missing.

[1] https://app.codecov.io/gh/pydoit/doit/compare/384

[bollwyvl]

Yeah, once some reports hit master, it starts working more.

[bollwyvl]

oh, merged! welp, added some badges on my push, feel free to steal!

[schettino72]

merged. thanks.