Update .travis.yml
 - move "Trigger Bitbucket" and "Trigger OSX build" to the
 after_script section so that their failures do not generate build
 failures (which will occur at lean-leo build)
 - move "install doxygen & graphviz" to the after_script to avoid a
 build failure due to the timeout of those package installations.
 - trigger both of OSX & Windows build+tests.
Add .travis.win.yml for windows build&test