Update Codecov upload API to v4 (replacement for #304)

[DilumAluthge]

Closes #304

Here is this diff for this PR versus PR #304: aa/codecov-v4...dpa/codecov-v4

[coveralls]

Pull Request Test Coverage Report for Build 933962705

• 12 of 12 (100.0%) changed or added relevant lines in 1 file are covered.
• 5 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.3%) to 90.64%

---

Files with Coverage Reduction	New Missed Lines	%
src/coveralls.jl	2	94.23%
src/codecovio.jl	3	86.87%

Totals
Change from base Build 926834392:	0.3%
Covered Lines:	184
Relevant Lines:	203

---

💛 - Coveralls

[codecov]

Codecov Report

Merging #318 (0b0e47e) into master (b79485e) will increase coverage by 0.33%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #318      +/-   ##
==========================================
+ Coverage   90.30%   90.64%   +0.33%     
==========================================
  Files           2        2              
  Lines         196      203       +7     
==========================================
+ Hits          177      184       +7     
  Misses         19       19              

Impacted Files	Coverage Δ
src/codecovio.jl	86.86% <100.00%> (+3.17%)	⬆️
src/coveralls.jl	94.23% <0.00%> (-1.93%)	⬇️

---

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[DilumAluthge]

@vtjnash @ararslan Take a look at this PR and let me know what you think.

[DilumAluthge]

Also, changing the version of the Codecov API that we use - is that a breaking change or a nonbreaking change?

[ararslan]

It's not really exposed to the user in terms of API, so IMO not breaking

[DilumAluthge]

It's not really exposed to the user in terms of API, so IMO not breaking

Sounds good to me!

I have bumped the minor version number.