Fix users image sometimes look ugly.
Fix blocked users are not properly treated.

close #56
Change error message in automatic updater.

Describe more details than previous one.
Add help link to authorization window.
Update dependent libraries except MahApps.Metro.

Latest version of MahApps.Metro is still unstable, so we decided not to update it.
Implement background image feature.
Add configuration for storing database file into another path.
Add setting for transparency of background image.
Implementing theme system...

Update theme definition.
Implement(ing) ResourceDictionary generator.
Update MahApps.Metro library.

Implementing theme system...
Change p/invoke method signature.
Implement "Attach Image from Clipboard".
change word of attach menu.
Add MahApps.Metro as submodule.
Implement database optimization feature.

Fix restart with maintenance mode sometimes not work properly.
Add description for restart with maintenance mode.
Commit related fix of MahApps.Metro library.
Fix: reply to message from context-menu is not working correctly.
WE CAN ROTATE TIMELINE!!!!!!!!!!!!!!!!!!!!!!!!!!!
Apply user agent configure for Twitter API requests.
Title bar uses TitleBarColor now instead of GlobalKeyColor.