docs(Modal): improve toggle example (reactstrap#1395)

Boolean states should be set with the previous state to avoid async state change issues.

Author: danielsogl

docs/lib/examples/Modal.js

@@ -14,9 +14,9 @@ class ModalExample extends React.Component {
   }
 
   toggle() {
-    this.setState({
-      modal: !this.state.modal
-    });
+    this.setState(prevState => ({
+      modal: !prevState.modal
+    }));
   }
 
   render() {

docs/lib/examples/ModalBackdrop.js

@@ -16,9 +16,9 @@ class ModalExample extends React.Component {
   }
 
   toggle() {
-    this.setState({
-      modal: !this.state.modal
-    });
+    this.setState(prevState => ({
+      modal: !prevState.modal
+    }));
   }
 
   changeBackdrop(e) {

docs/lib/examples/ModalCustomCloseButton.js

@@ -14,9 +14,9 @@ class ModalExample extends React.Component {
   }
 
   toggle() {
-    this.setState({
-      modal: !this.state.modal
-    });
+    this.setState(prevState => ({
+      modal: !prevState.modal
+    }));
   }
 
   render() {

docs/lib/examples/ModalCustomCloseIcon.js

@@ -14,9 +14,9 @@ class ModalExample extends React.Component {
   }
 
   toggle() {
-    this.setState({
-      modal: !this.state.modal
-    });
+    this.setState(prevState => ({
+      modal: !prevState.modal
+    }));
   }
 
   render() {

docs/lib/examples/ModalCustomTimeout.js

@@ -14,9 +14,9 @@ class ModalExample extends React.Component {
   }
 
   toggle() {
-    this.setState({
-      modal: !this.state.modal
-    });
+    this.setState(prevState => ({
+      modal: !prevState.modal
+    }));
   }
 
   render() {

docs/lib/examples/ModalDestructuring.js

@@ -16,9 +16,9 @@ class ModalExample extends React.Component {
     }
 
     toggle() {
-        this.setState({
-            modal: !this.state.modal
-        });
+        this.setState(prevState => ({
+            modal: !prevState.modal
+        }));
     }
 
     changeUnmountOnClose(e) {

docs/lib/examples/ModalExternal.js

@@ -14,9 +14,9 @@ class ModalExample extends React.Component {
   }
 
   toggle() {
-    this.setState({
-      modal: !this.state.modal
-    });
+    this.setState(prevState => ({
+      modal: !prevState.modal
+    }));
   }
 
   render() {

docs/lib/examples/ModalFadeless.js

@@ -14,9 +14,9 @@ class ModalExample extends React.Component {
   }
 
   toggle() {
-    this.setState({
-      modal: !this.state.modal
-    });
+    this.setState(prevState => ({
+      modal: !prevState.modal
+    }));
   }
 
   render() {

docs/lib/examples/ModalNested.js

@@ -18,9 +18,9 @@ class ModalExample extends React.Component {
   }
 
   toggle() {
-    this.setState({
-      modal: !this.state.modal
-    });
+    this.setState(prevState => ({
+      modal: !prevState.modal
+    }));
   }
 
   toggleNested() {