CRAN check tweaks

[slager]

I was curious about these CRAN check failures:

https://cran.r-project.org/web/checks/check_results_mop.html

 Version: 0.1.1
Check: code files for non-ASCII characters
Result: WARN
  Found the following file with non-ASCII characters:
    NAMESPACE
  Portable packages must use only ASCII characters in their R code and
  NAMESPACE directives, except perhaps in comments.
  Use \uxxxx escapes for other characters.
  Function ‘tools::showNonASCIIfile’ can help in finding non-ASCII
  characters in files.

The CRAN warnings were caused by ˆ instead of ^ in the NAMESPACE file.

When I fixed that character in mop_distance.R and re-ran devtools::document() to regenerate the NAMESPACE file, it fixed the first issue. However, because the regular expression now worked in exportPattern(), two undocumented helper functions were picked up by the permissive regex and added to the NAMESPACE file under exports, which in turn threw warnings in devtools::check because those two functions were not documented. I assume these two helpers were not intended to be documented or exported, so I just deleted the exportPattern() call from mop_distance.R, which resolved all of this.

The newest version of Roxygen2 also required a change to how the overall package was documented:
r-lib/roxygen2#1491

[marlonecobos]

Thanks for the fix. This was part of my to-do list. This should solve the warnings.