remove some preface wording for it is now almost complete.
also, fix #130
wrote explicit template argument specification for function templates.
fix preface
wrote condensed version of argument deduction.
declare it complete in the preface.
update README.
briefly explained the partial ordering.
This is not what I wanted to be.
fix wording nits
Merge pull request #131 from tzik/hiragana-to-kanji

fix wording nits
fix missing type in static_cast.
fix #132
Add gumroad link for purchase.
fix #133
fix https://github.com/EzoeRyou/cpp-book/issues/132#issuecomment-28174080