Implement React Context API

- Move API GET request to /v2/config out to the top level of our App.
- Store /v2/config response data in sessionStorage.
- Use Context API to pass down relevant data to Organizations component.
- Wrap our AnsibleSelect component as a context consumer and pass in the list of Ansible Environments of the logged in user.
- Clear sessionStorage object when user logs out.
- Update unit tests.

__mocks__/axios.js

@@ -1,5 +1,13 @@
-const axios = require('axios');
+import * as endpoints from '../src/endpoints';
 
+const axios = require('axios');
+const mockAPIConfigData = {
+  data: {
+    custom_virtualenvs: ['foo', 'bar'],
+    ansible_version: "2.7.2",
+    version: "2.1.1-40-g2758a3848"
+  }
+};
 jest.genMockFromModule('axios');
 
 axios.create = jest.fn(() => axios);
@@ -9,7 +17,16 @@ axios.create.mockReturnValue({
   get: axios.get,
   post: axios.post
 });
-axios.get.mockResolvedValue('get results');
+axios.get.mockImplementation((endpoint) => {
+  if (endpoint === endpoints.API_CONFIG) {
+    return new Promise((resolve, reject) => {
+      resolve(mockAPIConfigData);
+    });
+  }
+  else {
+    return 'get results';
+  }
+});
 axios.post.mockResolvedValue('post results');
 
 axios.customClearMocks = () => {