fix box_delete_folder()

[ijlyttle]

fix #197

The file and folder API calls return empty content, by Box' design.

In box_delete_folder(), we were trying to parse the empty content - leading to the error.

Fixed this, along with a stray documentation fix.

I found that using r string_side_effects() was not working within a {} structure, so I pasted it in manually.

[codecov-io]

Codecov Report

Merging #200 (eb3ea49) into master (8bbdea7) will increase coverage by 2.28%.
The diff coverage is 66.76%.

@@            Coverage Diff             @@
##           master     #200      +/-   ##
==========================================
+ Coverage   55.88%   58.16%   +2.28%     
==========================================
  Files          24       26       +2     
  Lines        1555     1788     +233     
==========================================
+ Hits          869     1040     +171     
- Misses        686      748      +62     

Impacted Files	Coverage Δ
R/boxr_add_description.R	0.00% <ø> (ø)
R/boxr_comment.R	0.00% <0.00%> (ø)
R/boxr_dir_verbs.R	99.10% <ø> (ø)
R/boxr_save_load.R	0.00% <0.00%> (ø)
R/boxr_search.R	0.00% <ø> (ø)
R/boxr_source.R	100.00% <ø> (ø)
R/boxr_upload_download.R	76.19% <ø> (ø)
R/utils-documentation.R	0.00% <0.00%> (ø)
R/zzz.R	13.33% <0.00%> (-0.96%)	⬇️
R/boxr_misc.R	46.08% <20.00%> (+1.44%)	⬆️
... and 16 more

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[nathancday]

Awesome bug/confusion fix and more test coverage?!? Love it.

[nathancday]

Did we double fix the conflicts? Sorry should have communicated better...but looks like this will build green and then we can Squash and Merge

[ijlyttle]

there's no problem at all - this is what I had intended to - to pull the other changes into this PR, make sure it all plays nicely together before merging.

sometimes the version numbers collide, that's all this is

[nathancday]

Got it okay, I saw the other was .13 and this was .14 so I was gonna merge in that order. Just didn't want to be making more work for you

[ijlyttle]

We're on our way!