Many bugfixes

• 8c7b145 Fixed a problem with the image creation in latest Chrome versions.
• f8705bb Dropzone.optionsForElement doesn't throw now when called with a form that has an input with the name 'id'
• 6286a57 On error, if a JSON object is returned, the 'error' attribute is now used as error message if available.
• a9e52d7 Select inputs with the multiple keyword work properly now.
• 797bae6 Dropzone.destroy() removes itself from Dropzone.instances now.
• 8802f46 Settings maxFiles to 0 works now.
• d7f6c41 Dropzone doesn't crash anymore if a form has an input field with name 'id'
• ac6e8f8 Displaying filesizes in Mebibyte, gibibyte, etc... now.