Add equals_na_linter

[jabranham]

Adds a linter that checks for e.g. x == NA rather than is.na(x). Added to default linters.

Let me know if something isn't clear or if I need to change something.

Closes #143

[codecov]

Codecov Report

Merging #326 into master will increase coverage by 0.22%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #326      +/-   ##
==========================================
+ Coverage   85.41%   85.64%   +0.22%     
==========================================
  Files          40       41       +1     
  Lines        2098     2131      +33     
==========================================
+ Hits         1792     1825      +33     
  Misses        306      306

Impacted Files	Coverage Δ
R/zzz.R	0% <ø> (ø)	⬆️
R/equals_na_lintr.R	100% <100%> (ø)

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[jimhester]

Thanks! Could you add a note to NEWS.md mentioning this addition with your GitHub handle and the issue number?

[jabranham]

Sure, done. I also regenerated the documentation.

Just FYI, the NEWS.md file starts with 1.0.1.9001, but that's smaller than what's in DESCRIPTION, which says 1.0.2.9000.

[gdequeiroz]

Just FYI, the NEWS.md file starts with 1.0.1.9001, but that's smaller than what's in DESCRIPTION, which says 1.0.2.9000.

@jabranham I noticed that. This version number shows when installing from gh: devtools::install_github("jimhester/lintr")

> packageVersion("lintr")
[1] ‘1.0.2.9000’

I don't know why. @jimhester can you help us here?

[jimhester]

It is just outdated in the NEWS file and needs to be updated.

[jimhester]

Thanks!