2.1.0: Support for XMP tags

Add support for XMP tags.

2.0.1: Support for IPTC tags and UMD

• Add support for IPTC tags.
• Remove need to instatiate the ExifReader object before use.
• Add UMD support (CommonJS, AMD and global).
• Convert project to JavaScript (ECMAScript 2015) from CoffeeScript, transpiling to ES5 using Babel.

v1.1.1: Make parsing of types and GPS tags more robust

Don't assume that we cannot encounter type IDs other than the specification
says. It does happen. Also, don't assume that the string values for
GPSProcessingMethod and GPSAreaInformation will always be correctly formatted
strings.