Dockerfile: remove ADD

ADD is not necessary since `google/nodejs-runtime` do `ONBUILD`
Merge pull request #5 from proppy/master

Dockerfile: remove ADD
Merge pull request #10 from rrch/master

Fix the path of the appengine library.
Merge pull request #11 from rrch/master

Rename CONTRIB.md to CONTRIBUTING.md.
Remove --server option from app deploy command.
Merge pull request #14 from rrch/f_readme

Remove --server option from app deploy command.