change PySide to PyQt5

[JaySon-Huang]

Here is a PR for using PyQt5 instead of PySide.

But I found that It maybe somewhat difficult for building PyQt5 under Python2 but not Python3. for example,

• the website of PyQt5 don't provide Binary Packages of windows for Python2, you need to build it from source by hand.
• when I build PyQt-5.3.2 for Python2 under Mac OSX, I happended to this compile problem: Issues building PyQt5 for Python3.4 in Ubuntu 14.04 caused by qprinter.h not found then pyuic5 error.(notice that it is not the newest version, for I had the not-so-new version of Qt5 compiled in my machine and I don't want to rebuild that. This problem seem fixed in the newest version of PyQt5)

Take care of this before accepting this PR ;)

[psifertex]

Yikes -- first, thanks very much for isolating the PyQt5 bits from the formatting changes. I wish I'd known about the lack of binary packages as I probably wouldn't have even mentioned considering an upgrade if I'd known.

Thanks for making sure to mention that, I think we'll probably just keep an eye out to see if anybody else publishes some premade 2.7 binaries before we upgrade. We definitely want to keep cross-platform support and maintain the relatively easy install process it has now (couple of binary dependencies or apt repository installs) and it looks like PyQt5 doesn't offer a mechanism for us to do that right now.