Pyslvs v20.07.0

Features:

• Fix canvas selection and display error.
• Generate calculation script after parser script. (github issue #35)
• Support parallel linkage. (github issue #36)
• Skip auto preview paths when saving file.
• Implement plotting function for slider paths.
• Implement final vector animation.
• Remove wavelet function.
• Add extra curve fitting function powered by SciPy.
• Some corrections of the main canvas.

Development:

• Extra SciPy requirement.
• Remove unessential __all__ list.