replace Link with Button in Course Home Dialog

refs: UIDEV-270

TEST PLAN:
- set-up: ensure you have Pages but no front page set
- navigate to a course
- select home from the sub navigation
- select "choose home page" from the right side bar
- see 'Front Page must be set first'
- next turn off the Front Page and repeat the steps to choose a
  home page... should see the name of the Front Page with a
  change link (since in context has been kept as a link that
  will underline by default)
- lastly, ensure 'Front Page must be set first' underlines if the
  user feature is turned on to underline links

Change-Id: I043ec7b44f9ad4f83d53f4089f490401900b15c2
Reviewed-on: https://gerrit.instructure.com/197974
Tested-by: Jenkins
Reviewed-by: Jennifer Stern <jstern@instructure.com>
QA-Review: Daniel Sasaki <dsasaki@instructure.com>
Product-Review: Pam Hiett <phiett@instructure.com>

app/jsx/courses/CourseHomeDialog.js

@@ -72,7 +72,7 @@ class CourseHomeDialog extends React.Component {
         <AccessibleContent>*</AccessibleContent>
         <ScreenReaderContent>
           <Link href={wikiUrl}>
-            {I18n.t('Front page must be set first')}
+            {I18n.t('Front Page must be set first')}
           </Link>
         </ScreenReaderContent>
       </span>
@@ -163,15 +163,17 @@ class CourseHomeDialog extends React.Component {
               null
             ) : (
               <div className="content-box-mini">
-              * <Link href={wikiUrl}>{I18n.t('Front page must be set first')}
-              </Link></div>
+              * <Button variant="link" href={wikiUrl} theme={{mediumPadding: '0', mediumHeight: '1.5rem'}}>
+                {I18n.t('Front Page must be set first')}
+                </Button>
+              </div>
             )
           }
 
         </ModalBody>
 
         <ModalFooter>
-          <Button onClick={this.props.onRequestClose}>{I18n.t('Cancel')}</Button>&nbsp;
+          <Button onClick={this.props.onRequestClose} margin="0 x-small">{I18n.t('Cancel')}</Button>
           <Button
             onClick={this.onSubmit}
             disabled={this.props.isPublishing && this.state.selectedDefaultView === 'modules'}

spec/javascripts/jsx/courses/CourseHomeDialogSpec.js

@@ -109,7 +109,7 @@ test('calls onRequestClose when cancel is clicked', () => {
       onRequestClose={onRequestClose}
     />
   )
-  const cancelBtn = dialog.find('Button').first()
+  const cancelBtn = dialog.find('Button').at(1)
   equal(cancelBtn.props().children, 'Cancel')
   cancelBtn.simulate('click')
   ok(onRequestClose.called)