Prevent scroll from completing a full cycle

Prevent scroll from completing a full cycle when quickly go to the next stop.
Otherwise, the animation will be queued and causes unexpected result.
Threshold implemented & fixed top option added

Threshold option was not implemented - update to implement
Option included to specify the css "top" distance for the fixed element
Add New Offcanvas Functionality

Allow Offcanvas to overlap content instead of pushing content.
Code Reduction
Add New Offcanvas Functionality 

Allow Offcanvas to overlap content instead of pushing content.
Add Vendor Prefixes for CSS transform

Add Vendor Prefixes for CSS transform.

Many thanks to @diggy for finding there was a problem in my Pen on Chrome.

Silly me for forgetting to put the vendor prefixes.
Update examples_offcanvas_javascript_options.html
Update examples_offcanvas_javascript_options.html

Oopsies, should be move not push
handle empty settings
Fix button background color not being used when defined in settings.
Added !important keyword to float: none; rule of centered columns in grid system
Currently selectors:
[class*="column"] + [class*="column"]:last-child { float: $opposite-direction; }
[class*="column"] + [class*="column"].end { float: $default-float; }
are more specific (specifity= 3) than rules for centered columns (specifity=2), and if centered
column is the last one in a row it will use f.e. float: right; rule instead of
float: none; from centered classes
- Allow to reuse dropdown-content element. If a target opened the dropdown, clicking another target will directly open the same dropdown element instead of just closing the previous one.
- Remove unnecessary call to this.close.call
Merge pull request #5086 from istrasoft/PR-dropdown-reuse

Allow to reuse dropdown-content element.
Merge pull request #5074 from danielsamuels/master

Fix button background color not being used when defined in settings.
Merge pull request #5083 from gastlich/master

Add !important keyword to float: none; rule of centered columns in grid system
Merge pull request #5067 from ibroadfo/master

handle empty settings in reveal
Merge pull request #4964 from glafarge/patch-2

Prevent scroll from completing a full cycle
Merge pull request #5035 from winghouchan/new-offcanvas-functionality

New offcanvas functionality
Merge pull request #5037 from winghouchan/update-offcanvas-docs

Update offcanvas docs
Fixing conflict