Repo cleanup to comply with catapult deploy process

- Added /dist/ folder to `.gitignore`
- Replaced references to version number with `XXX_VERSION_XXX`
- Replaced all-release `CHANGELOG.md` with per-release `changelog.txt`
- Removed `release.sh` script
- Added build task to `gulpfile.js`
- Updated `npm test` to build the distribution files before testing