Fix get_cid to return NA when query is NA and style update

[stitam]

Most of the PR is just style update according to lintr::lint(). The real difference is in line 59 of pubchem.R. get_cid() returned the Pubchem ID of sodium when the query was NA.

PR task list:

• Update NEWS
• Add tests (if appropriate)
• Update documentation with devtools::document()
• Check package passed

[codecov-io]

Codecov Report

Merging #223 into master will not change coverage by %.
The diff coverage is 0.00%.

@@          Coverage Diff           @@
##           master    #223   +/-   ##
======================================
  Coverage    0.00%   0.00%           
======================================
  Files          19      19           
  Lines        1582    1587    +5     
======================================
- Misses       1582    1587    +5     

Impacted Files	Coverage Δ
R/chemspider.R	0.00% <ø> (ø)
R/pubchem.R	0.00% <0.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 67b0603...9aff121. Read the comment docs.

[Aariq]

Nice! We should probably be careful about proper handling of NA for all get_ functions, not just because of the sodium issue (which has shown up before), but because we want them to be properly vectorized.