3.1.0

• dialog boxes are now draggable by default; see the newly added draggable property; see #38 and thanks LukeSavefrogs for suggesting this A LONG TIME AGO!
• added the onOpen event which triggers after the dialog box is made visible; see #39; thanks LukeSavefrogs for suggesting this A LONG TIME AGO!
• added the onBeforeClose event which triggers before the dialog is hidden; useful for validating input prompts and not closing the dialog box in case the input is not valid
• added placeholder property to be used with prompt type dialog boxes
• added prompt_rows which when set to a value greater than 1 will turn the input element in a prompt dialog box to a textarea
• fixed bug where page scrolling was not disabled when opening modal dialog boxes even though disable_page_scrolling was set to true by default