Make distanceBetweenPoints work on MacOS

[p-j-smith]

Fixes #56

Changes made:

• Added a private function private/initialiseGeodesic for initialising the geodesic library
• It determines the platform (macos or other unix) and then loads the appropriate library file
• Note - Windows is not currently supported
• Added tests for distanceBetweenPoints, which calls private/initialiseGeodesic. In these tests is an example of how to write very basic tests for functions that create plots (the plot should not be displayed)
• Added tests for private/distBetweenPoints (which I initially thought was called by distanceBetweenPoints when method is linear). This provides an example of how to tests the functions in the private directory (by changing to this directory before calling the required function)

[codecov[bot]]

Codecov Report

Merging #57 (ae6639e) into develop (69ee22c) will increase coverage by 4.40%. The diff coverage is 73.33%.

@@            Coverage Diff             @@
##           develop     #57      +/-   ##
==========================================
+ Coverage     0.27%   4.67%   +4.40%     
==========================================
  Files          134     135       +1     
  Lines         7009    7012       +3     
==========================================
+ Hits            19     328     +309     
+ Misses        6990    6684     -306     

Impacted Files	Coverage Δ
HoleCutter.m	0.00% <0.00%> (ø)
private/initialiseGeodesic.m	70.00% <70.00%> (ø)
distanceBetweenPoints.m	100.00% <100.00%> (+100.00%)	:arrow_up:
private/distBetweenPoints.m	100.00% <100.00%> (+100.00%)	:arrow_up:
getMesh.m	29.78% <0.00%> (+29.78%)	:arrow_up:
private/colorspec2rgb.m	36.84% <0.00%> (+36.84%)	:arrow_up:
private/geodesic_delete.m	38.46% <0.00%> (+38.46%)	:arrow_up:
private/findclosestvertex.m	43.24% <0.00%> (+43.24%)	:arrow_up:
drawMap.m	49.42% <0.00%> (+49.42%)	:arrow_up:
private/geodesic_create_surface_point.m	60.00% <0.00%> (+60.00%)	:arrow_up:
... and 12 more

---

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 69ee22c...ae6639e. Read the comment docs.