Adds tests for prepatch, removes duplicate preminor and premajor tests. Adds fix for prepatch run on a prerelease not bumping to the next patch version similar to preminor and premajor. Fixes #86
…W.Y.Z` Fixes #74.
Also, the utility function that gtr and ltr use, `outside(version, range, hilo)`
gtr(version, range): Return true if version is greater than all the versions possible in the range.