Use preversion script instead of prepublish (palantir#1)

* Use preversion script instead of prepublish

`prepublish` is (confusingly) [run before install](npm/npm#3059), and fails because `npm-run-all` isn't installed yet. This makes it difficult to install the initial packages to dev on this project. Using `preversion` seems like a better fit

* Update package.json

Also add `npm-run-all` dep

package.json

@@ -13,13 +13,14 @@
     "compile": "tsc -p ./",
     "copy": "cp -f package.json build/src/rules/",
     "lint": "tslint 'src/**/*.ts'",
-    "prepublish": "npm-run-all clean test copy",
+    "preversion": "npm-run-all clean test copy",
     "test": "npm-run-all build test-rules",
     "test-rules": "node ./build/test/ruleTestRunner.js"
   },
   "devDependencies": {
     "colors": "^1.1.2",
     "glob": "^7.0.3",
+    "npm-run-all": "^2.1.2",
     "path": "^0.12.7",
     "tslint": "^3.11.0",
     "typescript": "^1.8.10"