Merge pull request #123 from GuillaumeGomez/master

add gvalue + support for treestore
fix Widget trait implementation
This trait was implemented for a lot of struct who was not widgets
this fix this by removing the implementation for the given struct and fixing
the resulting problems.
fix travis build
begin implementation of safe signals
add impl_*_event macros, for implements invents
for the moment only events for widget and existing events are binded.
Merge pull request #122 from jeremyletang/wip-signals

fix signals
try fix c_long / c_ulong cast for 32bit linux.
Work in progress on TextView widget