Update eslint rules

Changed rules to fix conflicts with flow

.eslintrc.js

   },
   rules: {
     'react/jsx-filename-extension': [1, {extensions: ['.js', '.jsx']}],
+    'react/static-property-placement': [2, 'static public field'],
     'flowtype/define-flow-type': 1,
     'flowtype/no-mixed': 2,
     'flowtype/no-primitive-constructor-types': 2,
       onlyFilesWithFlowAnnotation: false,
     },
   },
+  globals: {
+    fetch: false,
+    Headers: false,
+  },
 };