Remove all unnecessary files from npm package

Author: nkbt

.npmignore

@@ -1,8 +1,14 @@
-.DS_Store
 *.log
-examples
-test
-coverage
-_book
-book.json
-docs
+/.*/
+/_book/
+/coverage/
+/docs/
+/examples/
+/test/
+/.eslint*
+/.flowconfig
+/.gitignore
+/.npmignore
+/.travis.yml
+/book.json
+/webpack.*