Add FileChooserWidget and initial FileChooser bindings.
Add additional GTK 3.10 binding support.
Move 3.10-specific type casting calls to correct file.
Take 2.
Add GtkRevealer bindings.
Use correct new function.
Add margin getters and setters.
Add GtkAssistant bindings.
Use map to lookup GValue to Go variable marshalers.

This change removes the switch in Value.GoValue, replacing it with a
map lookup of the value's fundamental type to find and execute a
marshaling function to perform the marshal.  No changes have been made
to the marshaling itself, and should behave identically to the
previous implementation.

This is a step towards completing #44.  When registering a type,
marshaler and unmarshaler funcs should be provided as well.  By moving
the mashaler lookup to a package-global map, externally-registered
marshalers may be run when looked up with a matching GType.
Fix a comment.
Shut golint up a little.
Unexport the ObjectNew function.

This function did not match the behavior of the similarily-named
g_object_new() and required passing in a C pointer to an
already-created GObject.
RefSink and Unref (at GC) marshaled Objects.
Move object ref+unref handling to GoValue.

This changes the previous commit to RefSink and Unref all GObject
wrapper types if they satisify the IObject interface (implemented by
Object and all types embedding an Object).

When custom marshalers are able to be registered (see #44), this will
mean that marshaling funcs will not be required to (and should be
discouraged from) handling the refcounts themselves.
Actually return the correct values.
Fix some compile errors likely introduced in go tip.
Add MenuButton bindings.
Make MenuShell.Append's type checks stricter.

gtk_menu_shell_append and related GtkMenuShell methods take a
GtkWidget * as an argument but the documentation specifies that the
child must be a GtkMenuItem (or subclass).  This change modifes the
Append method to instead take a new interface type, IMenuItem, that is
implemented by all menu item widgets (including MenuItem and
SeparatorMenuItem).

This is technically an API break but should be source compatible with
any previous correct usage of Append.
Add toWidget methods for new IMenu* interfaces.

This uses the toWidget methods from the embedded Widget, rather than
calling toMenu/toMenuItem and using unsafe to switch the pointer to a
*C.GtkWidget.
Add RadioButton bindings.

Closes #38.