show flow warnings and fixes all reported ones (#1832)

Author: IvanGoncharov

.flowconfig

@@ -10,6 +10,8 @@
 [libs]
 
 [options]
+include_warnings=true
+module.use_strict=true
 suppress_comment=\\(.\\|\n\\)*\\$FlowFixMe\\($\\|[^(]\\|(\\(<VERSION>\\)?)\\)
 suppress_comment=\\(.\\|\n\\)*\\$FlowIssue\\((\\(<VERSION>\\)?)\\)?:? #[0-9]+
 suppress_comment=\\(.\\|\n\\)*\\$DisableFlowOnNegativeTest

src/type/__tests__/predicate-test.js

@@ -605,7 +605,6 @@ describe('Directive predicates', () => {
     });
 
     it('returns false for directive class (rather than instance)', () => {
-      // $DisableFlowOnNegativeTest
       expect(isDirective(GraphQLDirective)).to.equal(false);
       expect(() => assertDirective(GraphQLDirective)).to.throw();
     });

src/utilities/__tests__/buildClientSchema-test.js

@@ -548,7 +548,6 @@ describe('Type System: build schema from introspection', () => {
       const introspection = introspectionFromSchema(dummySchema);
 
       expect(introspection).to.have.nested.property('__schema.queryType.name');
-      // $DisableFlowOnNegativeTest
       delete introspection.__schema.queryType.name;
 
       expect(() => buildClientSchema(introspection)).to.throw(
@@ -705,7 +704,6 @@ describe('Type System: build schema from introspection', () => {
         name: 'SomeDirective',
         locations: ['QUERY'],
       });
-      // $DisableFlowOnNegativeTest
       delete someDirectiveIntrospection.locations;
 
       expect(() => buildClientSchema(introspection)).to.throw(
@@ -721,7 +719,6 @@ describe('Type System: build schema from introspection', () => {
         name: 'SomeDirective',
         args: [],
       });
-      // $DisableFlowOnNegativeTest
       delete someDirectiveIntrospection.args;
 
       expect(() => buildClientSchema(introspection)).to.throw(