Update version format for usage with semver

Tracking the version under one `-prerelease` channel allows other packages to depend on `^0.1.0-prerelease` for the most up to date version.

Track the git sha for the release in package.json

Reuse the json package needed for writing the sha to retrieve the package.json version field

.travis.yml

@@ -23,7 +23,7 @@ after_script:
     # Authenticate NPM
     echo "//registry.npmjs.org/:_authToken=\${NPM_TOKEN}" > .npmrc
     # Set version to commit SHA
-    npm --no-git-tag-version version $(node -p -e "require('./package.json').version")-${TRAVIS_COMMIT:0:5}
+    npm --no-git-tag-version version $($(npm bin)/json -f package.json version)-prerelease.$(date +%s)
     npm publish
     # Publish to gh-pages as most recent committer
     git config --global user.email $(git log --pretty=format:"%ce" -n1)

package.json

@@ -11,6 +11,7 @@
   },
   "main": "./dist.js",
   "scripts": {
+    "version": "./node_modules/.bin/json -f package.json -I -e \"this.repository.sha = '$(git log -n1 --pretty=format:%H)'\"",
     "prepublish": "make build",
     "start": "make serve",
     "test": "make test"
@@ -24,6 +25,7 @@
     "babel-preset-es2015": "6.9.0",
     "eslint": "2.7.0",
     "gh-pages": "0.11.0",
+    "json": "9.0.4",
     "json-loader": "0.5.4",
     "lodash.defaultsdeep": "4.6.0",
     "raw-loader": "0.5.1",