QML error fix with PyQt5.3

Fix QML error when load the TimelineTools and get QtQuick2 from PyQt5.3
QML MainWindow: add file > new menu

fix #63
ButtleData: fix newData Slot

Emit signal to get the save button disable when create a new graph.
QML Graph: clean

In the Graph toolbar, apparently the fileDialogs of "new" (Ctrl+N) and
"open" (Ctrl+O) actions had problems (need to call open() twice), but
that's not the case.
add flake8 check on travis
Merge branch 'develop' of https://github.com/buttleofx/ButtleOFX into dev_QMLfix
Merge pull request #114 from buttleofx/dev_QMLfix

Dev QML - add file > new menu (#63)