add parameter pack example for generic lambda.
Add gumroad link for my C++11 textbook.
Merge branch 'gh-pages' of https://github.com/EzoeRyou/kabukiza-tech2-slide into gh-pages
fix date.
fix page 55
fix page 57
fix page 61
support lower resolution.
Merge remote-tracking branch 'upstream/gh-pages' into gh-pages