Add the class Post and some functions.
Separate filtering posts from generating an HTML.
Delete unused functions.
Simplification.
Separate a code generating an HTML form from an HTML here document.
Shorten an expression to be substituted in a string.
Fix a missing argument.
Rename a function.
Enable highlighting matched substrings again.
Introduce a DB class 'FsDB'.
Separate to_html method from the Post class.
Group functions related to htmlization of posts into a module 'BBS'.
Merge branch 'refactoring'