Lock npm packages version number on apollo-example

[thiago-soliveira]

Running yarn install on apollo-server example is not working.

After some digging, these are the problems I've found:
1 - ts-node was missing.
2 - graphql-schema-decorator was missing.
2 - apollo-server-hapi did not respect semver. From 1.1.7 to 1.3.2 backwards-compatibility wasn't maintained.

So, apart from adding missing packages, I'd like to suggest locking npm packages version numbers.