Updated mime.js:

- Added iconv
- Fixed MIME type default fallback
Updated mime.js: Added util fn for utf8 -> bytes
Updated mime.js: Fixed a context reference bug
Updated mime.js: Added iconv to base64 en/decoding
Updated mime.js: encodeWord() adjusted to iconv use
Updated mime.js: Fixed folding regex in decodeQP()
Updated mime.js: Updated encodeQP()
Updated mime.js: Removed unescape from decodeQP()
Updated package.json
Added tests
Added Travis CI