#152: Ensured at least one ColumnSize must be set, both during Construction and with setters. Had to remove constructor with the Widget varargs constructor as the signature would be identical to the ColumnSize varargs constructor. Widgets can still be added after construction using the add method.
#152: Add back (with adjustment) convenience constructor for adding widgets. Remove unneeded @UiConstructor annotation
Corrected JavaDoc
#152: Remove incorrect call to setStyleName
Merge pull request #188 from smallporgies/master

#152: Ensure at least one ColumnSize must be set
Code formatting
Added Radio, InlineRadio and InlineCheckBox widgets
Code formatting & code style issues
Added reference to Contributing wiki page
Missing period
Alert is now properly detached from parent when closed
Merge pull request #193 from servy/alert_fix

Alert is now properly detached from parent when closed