Tips section added, old pages removed

4-7-saving-images.md

-# Saving as images & videos
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-| [Previous Page](4-6-time-series-data) | [Home (Table of Contents)](home) | [Next Page](4-8-multiple-windows) |
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4-8-multiple-windows.md

-# Side-by-side comparison using two windows
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-> NOTE: You can actually create as many windows as you want.
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-You do this...
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-| [Previous Page](4-7-saving-images) | [Home (Table of Contents)](home) | [Next Page](4-9-speed-up-repetitions) |
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4-9-speed-up-repetitions.md

-# How to speed up repeated tasks
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-| [Previous Page](4-8-multiple-windows) | [Home (Table of Contents)](home) | [Next Page](5-1-acknowledgement) |
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