Since HashSet is not thread-safe, getting a Set from ConcurrentHashMa…

…p which is thread-safe.

Fixed a typo

Updated documentation for 1.0.0 release

Added ProGuard rules to the library. No need to manually add the ProG…

…uard configuration anymore.

Added a CHANGELOG
Updated README

Closing streams when encoding and decoding SerializableCookie

Added a fixed serialVersionUID to SerializableCookie (to avoid proble…

…ms when it is generated).

Related with Issue franmontiel#4.

Merge branch 'rciovati-fix/remove-manifest-attributes'