Integer division fixed for py3

[P-D-E]

Integer division fixed for py3 in GUISimpleListPicker.viewMove, it caused a bug scrolling after the last text page in the Introduction. (py2: 4 / 5 -> 0; py3: 4 / 5 -> 0.8)

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Please answer the following:

Code Changes:

• [x] Have the PR Validation Tests been run? See https://github.com/vegastrike/Vega-Strike-Engine-Source/wiki/Pull-Request-Validation
• [ ] This is a documentation change only

Issues:

• Please list any related issues https://github.com/vegastrike/Assets-Masters/issues/30

Purpose:

• What is this pull request trying to do? Fixing the Intro Monologue crash
• What release is this for? 0.8.x
• Is there a project or milestone we should apply this to? 0.8.x