removes old issue template

ISSUE_TEMPLATE.md

-#### Problem:
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-#### JSBin/JSFiddle demonstrating the problem:
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-Before you create an issue, check it:
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- 1. Try [master](https://github.com/SortableJS/Sortable/tree/master/)-branch, perhaps the problem has been solved;
- 2. [Use the search](https://github.com/SortableJS/Sortable/search?q=problem), maybe we already have an answer;
- 3. If not found, create an example on [jsbin.com (draft)](http://jsbin.com/vojixek/edit?html,js,output) and describe the problem.
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-Bindings:
- - Angular
-   - 2.0+: https://github.com/SortableJS/angular-sortablejs/issues
-   - legacy: https://github.com/SortableJS/angular-legacy-sortablejs/issues
- - React
-   - ES2015+: https://github.com/SortableJS/react-sortablejs/issues
-   - mixin: https://github.com/SortableJS/react-mixin-sortablejs/issues
- - Polymer: https://github.com/SortableJS/polymer-sortablejs/issues
- - Knockout: https://github.com/SortableJS/knockout-sortablejs/issues
- - Meteor: https://github.com/SortableJS/meteor-sortablejs/issues