Merge pull request #12 from hotwatermorning/build_documents

Build documents from 22e891a3e46bef20596c1dee09b1da14a1fe9c17
add following accessor: optional_front, optional_back, optional_at.
fixed English.
fixed English.
Fix section names.
Fix descriptions.
Fix text formats
Add a missing namespace section.
Fix sample codes.
Build html documents from 16f4b6bf45ba9ac9a1f4b951d61707e9b2a6705f
Remove unused files.