ChakraCore NuGet: Follow-Up Items

Follow-up from #85

### Possible Work Items
- [ ] Include a `change.json` file in the NuGet packages to provide easily-accessible information about the commit the package was built from.
- [ ] Integrate with [MyGet's SymbolSource infrastructure](http://docs.myget.org/docs/reference/symbolsource) to enable debugging when needed without having to ship the debugging symbols with every binary package.
- [ ] Split NuGet feeds for entire set of dev files versus just what is needed for deployment. (REVIEW: Is this useful? Possibly for scenarios which require low disk usage and/or low-bandwidth for downloading packages. What does "just deployment" look like?)

### Future Work (maybe split into a new issue)
- NuSpec for Linux and OS X Native Development
- NuSpec for Linux and OS X .NET Development
- MyGet feed for preview builds of Linux targeted binaries
- NuGet feed for official Linux and OS X builds

### Related to releases but not NuGet:
- [x] (See https://github.com/Microsoft/ChakraCore/issues/2278): Make xplat binaries more easily available to xplat users.

/cc (interested ChakraCore maintainers) @digitalinfinity @boingoing @liminzhu
/cc (folks from #85) @ormico @matthargett @pre10der89 @resnyanskiy @gulbanana @jimmcslim @Oceanswave