React Async v4 (#21)

This is a major update making `useAsync` the primary interface, stabilizing its API. It also adds the `useFetch` hook for more convenience working with HTTP requests. Furthermore there's several breaking changes: 

- `deferFn` now receives an `args` array as the first argument, instead of arguments to `run` being spread at the front of the arguments list. This enables better interop with TypeScript. You can use destructuring to keep using your existing variables.
- The shorthand version of `useAsync` now takes the `options` object as optional second argument. This used to be `initialValue`, but was undocumented and inflexible.

Author: ghengeveld

.eslintrc

@@ -16,7 +16,7 @@
   },
   "settings": {
     "react": {
-      "version": "16.3"
+      "version": "16.8"
     }
   }
 }

.travis.yml

@@ -4,6 +4,6 @@ node_js:
 cache:
   directories:
     - node_modules
-script: npm run test:compat && npm run test:hook
+script: npm run test:compat
 after_success:
   - bash <(curl -s https://codecov.io/bash) -e TRAVIS_NODE_VERSION