Add notes on new usability features to README.md

[SudoBobo]

New features should be described. Related to #59 and #60. List of new features:

1. Zero config
2. require('graphql').execute()/compile() functionality
3. GraphiQL
4. Config complimentation
   Also I propose to re-work the whole README so it can be used by any new user of our lib. Add 'Usage' section and so on.

[Totktonada]

@SudoBobo It seems that README now have the information you mentioned. Do you plan to do some more work in the scope of this issue or it can be closed?

[SudoBobo]

@Totktonada There is still nothing on config complementation (case when we do local gql_wrapper = graphql.new({connections = connections})) I'll add it today and when we could close the ticket.

[Totktonada]

@SudoBobo Please, base your branch on PR #168, because I’ll merge it soon.

[SudoBobo]

@Totktonada ok

[Totktonada]

I'm going to archive the repository. I'll proceed as follows:

• Mark all open pull requests with the archived label and close.
• Mark all open issues with archived and wontfix labels and close.
• Archive the repository.

Consider the following projects:

• https://github.com/tarantool/graphql
• https://github.com/tarantool/graphqlapi
• https://github.com/tarantool/graphqlide