[ZEPPELIN-2516] Set offset, tolerance for navbar, actionbar hiding

### What is this PR for?

Set offset, tolerance for navbar, actionbar hiding. See the attached screenshots.

### What type of PR is it?
[Bug Fix]

### Todos

NONE

### What is the Jira issue?

[ZEPPELIN-2516](https://issues.apache.org/jira/browse/ZEPPELIN-2516)

### How should this be tested?

Refer the screenshots.

### Screenshots (if appropriate)

#### Before

![2516_before](https://cloud.githubusercontent.com/assets/4968473/25854795/4221f2e8-350c-11e7-8ce9-447f2f77d489.gif)

#### After

![2516_after](https://cloud.githubusercontent.com/assets/4968473/25854802/476af2b8-350c-11e7-8fea-8e1d94fcafc4.gif)

### Questions:
* Does the licenses files need update? - NO
* Is there breaking changes for older versions? - NO
* Does this needs documentation? - NO

Author: 1ambda <[email protected]>

Closes apache#2325 from 1ambda/ZEPPELIN-2516/set-offset-tolerance and squashes the following commits:

5d9317c [1ambda] fix: Set offset, tolerance

zeppelin-web/src/app/notebook/notebook-actionBar.html

@@ -11,7 +11,7 @@
 See the License for the specific language governing permissions and
 limitations under the License.
 -->
-<headroom class="noteAction"
+<headroom tolerance="10" offset="30" class="noteAction"
           ng-show="note.id && !paragraphUrl">
   <h3>
     <div style="float: left; width: auto; max-width: 40%"

zeppelin-web/src/components/navbar/navbar.html

@@ -10,7 +10,7 @@
 limitations under the License.
 -->
 
-<headroom class="navbar navbar-inverse navbar-fixed-top"
+<headroom tolerance="10" offset="30" class="navbar navbar-inverse navbar-fixed-top"
           style="display: none;" role="navigation"
           ng-class="{'displayNavBar': !asIframe}">
   <div class="container">