Changed the term `fold` to `collapse` as `fold` is widely used for word-wrapping.
Moved the code that constructs a collapsible section title block into a separated new method to make each method smaller.
- Supported the `show_toggle_all_button` argument that inserts a button to toggle all collapsible sections.
- Tweaked the styling of collapsible sections for WordPress v3.7.x or blow. Resolves #169.
Add the examples for the `show_toggle_all_button` argument.
- Advanced the version number to help identify the changes.
- Generated the minified version to reflect the changes.