refactoring of remainder of history into skeleton/slots
refactoring and cleanup of the remainder of history text into skeleton/slots
refactored timeline class to use mixin along with mixin updates to part titles and preface
Merge pull request #413 from Connexions/history-refactor

Refactoring of remainder of History text into skeleton/slots
fix for figure timeline comments indentation
Merge pull request #414 from Connexions/history-refactor

History refactor indentation fix for figure timeline comments
Change .style(), .style(...), .style(@kind...) to .style(any...), refactored the remaining pieces at the end of the precalculus skeleton.
refactoring of psychology sections into skeleton/slots
refactoring of chapter objectives for psychology text
Merge branch 'master' into precalculus-refactor
fixed colophon h1.title conflict with initial test merge with precalc-refactor
Merge pull request #415 from Connexions/precalculus-refactor

Precalculus Skeleton/Slot refactoring
refactoring of psychology text into skeleton/slots plus bugfixes
Merge branch 'master' into psychology-refactor