Substantial internal changes to the plugin.

Change in library

The plugin now makes use of Gson for saving session data.
This change still keeps the version backward-compatible with 0.1.0.
The old session data may not be loaded correctly by the plugin. Most probably the backward compatibility is lost.

Change in License

The plugin is now licensed under GPLv3

Changelogs

• Implemented reload( #6 )
• Implemented vote cancelling (#4 )
• Implemented session deletion ( #3 )
• Implemented automatic saves ( #5 )
• Use Gson for generating session data file.