LICENSE: Correct copyright.

Save user-provided data by default, add `-i` option.

Add option to include cover page.

Add Structural Semantics Vocabulary to References.

Return to using `for F in` instead of `while read -r F` for now.

Fix missing variable argument to `while read -r` calls.

Add .shellcheckrc file to disable certain messages.

Change usages of `for F` to `while read` where appropriate.

Improve `create_epub` function.

* Handle failure to cd to $WORK_DIR.
* Use subshell to avoid needing to cd back.

Quote default assignments.

Add `-r` option to `read` calls.

Handle any incorrect number of arguments to script.

Move zipping process to a function.

Check for availability of zip(1).

Replace `which` with `command -v`.

Merge pull request #1 from u9000-Nine/patch-1

Replace `echo -n` with `printf`.

Replace echo -n

Use `printf %s` instead of `echo -n`. (printf alternative to `echo` is `printf '%s\n'`)

Remove `-p` option from calls to `read`, for portability.

Address various issues reported by shellcheck.

Fix typos and formatting.