feat: fix wrong contributing urls again. sigh

feat: update contributing with proper url, and also HOPEFULLY fixes s…

…emantic-release.

Don't save starting properties in the Tween constructor.

fix: Allow npm scripts to be run on Windows by removing occurrences o…

…f "/c/Users/mike/Documents/repo/tween.js".

fix: Don't interpret string values as relative if they do not start w…

…ith a sign. Closes tweenjs#239 and also add tests to define the behaviour of relative values, closes tweenjs#243

fix: do not interpolate properties that do not exist in the source ob…

…ject. Closes tweenjs#244

fix: add a bogus version number in package.json so the library can be…

… installed using the git protocol (e.g. from github). Closes tweenjs#242

fix: implement fix from @benfoxall for 'chained tweens get out of syn…

…c with sporadic updates'. Closes tweenjs#187

feat: Run style tests when running the tests too, via JSCS - closes t…

…weenjs#222

feat: run correctness test when running tests, via jshint. Closes twe…

…enjs#225