I downloaded the prepackaged .zip file of the mapstraction library from Github, and placed that folder (renamed to 'mapstraction') inside the mapstraction module folder. After maps would not show up, I looked inside the module code, and found that the .js files for the mapstraction module should actually be in path/to/modules/mapstraction/mapstraction/source/[file].js.

The documentation should be updated to reflect this fact.