Add support for SSR and Suspense.

[parkerziegler]

urql v1.1.0 introduced server-side rendering and basic support for Suspense on the server via react-ssr-prepass. With the new goal being to bind reason-urql's next version to urql v1.1.3, this becomes a major priority for us. The responsibility on the binding side is actually quite small (relatively) here:

• Upgrade urql dependency to v1.1.3. This is the v1.1.x version that contains several important bug fixes before jumping to 1.2.0, which may require a change to the bindings to work properly.
• Add suspense flag to Client configuration.
• Create bindings for react-ssr-prepass – this should be done in a separate repo at FormidableLabs/bs-react-ssr-prepass.
• Bind ssrExchange.
• Add unit tests for ssrExchange.
• Create a working NextJS example – we'll likely want to copy the one Zeit has already in place for starters: https://github.com/zeit/next.js/tree/canary/examples/with-reasonml

[parkerziegler]

For those tracking this issue, bs-react-ssr-prepass is live here: https://github.com/FormidableLabs/bs-react-ssr-prepass

[parkerziegler]

Latest PR for this issue merged #111. WIll be released in v1.1.0.

[parkerziegler]

An example using reason-urql with Next is available here: https://github.com/parkerziegler/reason-urql-ssr We'll link this example in the README as well.