Clean dist before build

Author: wojtekmaj

package.json

@@ -8,8 +8,9 @@
     "build": "yarn run build-js && yarn run copy-styles && yarn run build-styles",
     "build-js": "babel src -d dist --ignore __tests__",
     "build-styles": "lessc ./dist/DateTimePicker.less ./dist/DateTimePicker.css",
+    "clean": "rimraf dist",
     "copy-styles": "node ./copy-styles.js",
-    "prepublishOnly": "yarn run build",
+    "prepublishOnly": "yarn run clean && yarn run build",
     "test": "yarn run test-eslint && yarn run test-jest",
     "test-eslint": "eslint src/ test/ --ext .jsx,.js",
     "test-jest": "jest",
@@ -72,7 +73,8 @@
     "less": "~3.7.1",
     "react": "^16.4.0",
     "react-dom": "^16.4.0",
-    "react-test-renderer": "^16.4.1"
+    "react-test-renderer": "^16.4.1",
+    "rimraf": "^2.6.2"
   },
   "peerDependencies": {
     "react": ">=15.5",

yarn.lock

@@ -4153,7 +4153,7 @@ right-align@^0.1.1:
   dependencies:
     align-text "^0.1.1"
 
-rimraf@^2.2.8, rimraf@^2.5.4, rimraf@^2.6.1:
+rimraf@^2.2.8, rimraf@^2.5.4, rimraf@^2.6.1, rimraf@^2.6.2:
   version "2.6.2"
   resolved "https://registry.yarnpkg.com/rimraf/-/rimraf-2.6.2.tgz#2ed8150d24a16ea8651e6d6ef0f47c4158ce7a36"
   dependencies: