Javascript Highlighting Support and Image Fix

This release is ahead of the Tcllib release. It contains the following fixes and additions.

• fix for image tag
• adding header and footer support
• adding javascript (single and multiple file support)
• adding code highlight support
• adding css support for multiple files
• fix for library Markdown bugs in handling of code fences
• adding standalone binary mkdoc.bin, see below

To use the binary as application, just download the file mkdoc-0.8.0 (<100kb), make it executable, rename it to mkdoc and copy it to a folder belonging to your PATH. The file contains all required Tcl libraries (fixed markdown, yaml, cmdline, textutil) so that for running the program just a recent Tcl interpreter (8.5+) is needed.