* Enable declarationMap in tsconfig.json
See http://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-9.html
* Add apollo-server-caching package and improve typings
* Remove superfluous test steps
* Add .npmignore to apollo-server-caching
* Add apollo-server-env and apollo-datasource-rest packages
* Fix broken imports
* Use prepublish instead of prepare
* cache is now passed to data sources from ApolloServer constructor
* fix Object.values to use the object passed in rather than this
* add initial datasource test
* docs: initial data source documentation
* docs: initial data source documentation
* compiles and documentation now highlights code in data-sources.md
* Some changes to the data source docs
- Actually call validationDidStart and parsingDidStart.
- Use new graphql-extensions API which:
- replaces fooDidEnd with a handler returned by fooDidStart
- adds options to various methods
- has a new willSendResponse method
- requires you to construct the extension objects yourself (but make
the external API for specifying extensions to ApolloServer be
factories, because extensions are per request)
- Make a better effort at consistently calling end handlers even on error
