Tune first Foundations several segments

Add diagrams, additional slides with topic headers, diagrams, and
details labs
Add SVG logos

Git, GitHub logos for “slide” use
Add overrides for "slide" content scaling
Separate GitHub Web Flow from PR intro steps
Aggregate similar topics, add back major topic headings
Add Visualizations chapter heading
Tune title plurals
Adjust wording, additional "Detail" content
Merge pull request #226 from github/more-foundations-tuning

Update Foundations with final chapter sections and tune up
Bullet benefits of local repos for reader parsing

Local repo benefits into a list to make it more
digestible compared to a list written in sentences.

Swap Subscribing/Unsubscribing in Ecosystem
since you undo something after you do it.

Does not assume who Cameron is, using first and last names.
Add build-step Merge diagrams
Add separate slide build-steps for tracking states
Add lab first draft to "undo" section
Merge pull request #228 from github/intermediate-adjustments

Intermediate diagrams and missing content additions
Merge pull request #227 from randomecho/foundation-local-repo-benefits

Bullet benefits of local repos for reader parsing
Merge branch 'master' into heading-level-consistency

Conflicts:
	foundations/index.md