Updated the WebWorldWind npm project's build dependencies to ensure compatibility with the latest version of Node.js, Grunt, Karma, and Jasmine.
While changes like this are always worthwhile, I'm making it now to ensure that the original WebWorldWind source and its accompanying npm project will continue to operate for as long as possible after the [WorldWind project's suspension on April 5, 2019](https://worldwind.arc.nasa.gov/news/2019-03-08-suspension-notice). Secondary goals are eliminating all npm audit warnings from old versions of libraries used to build WebWorldWind (i.e. the devDependencies) and ensuring that unit tests continue to operate.
Summary of changes:
- WebWorldWind now builds with Node.js 10.15.3 LTS and 11.12.0. The README file and the Travis CI configuration file reflect that.
- All npm devDependencies, used for building the WorldWind project, are updated to the latest version available as of this pull request.
- All npm security audit vulnerabilities are addressed.
- Subtle errors in unit tests fixed. WorldWind's geometric unit tests erroneously modified global variables, such as Location.ZERO. These values shouldn't be encoded as global variables, but solving that is out of scope here. Previous versions of Jasmine concealed this problem but these unit tests fail with Jasmine 3.x, likely due to a change in the Jasmine interpreter lifecycle between tests.
