Move installation guide out of README.

Provide just the basic info and reference the wiki guide for details.
Add --debug option.

Just a useful shorthand during development.
Implement --message option.

To allow for simpler way to supply the old version warning message.
Move Docs app related ruby code to web/ subdir.

Cleaning up the top JSDuck namespace even more.

I always had some trouble finding all the different web-output-related
classes.
Save CSS from tags into separate CSS file.

MD5-rename the file like with data.js file.
Then link it from index.html.

Also reorganize the Web::Writer class.
Save the MD5-renamed files to a local hash instead of
polluting the Options object - then pass the hash directly
to IndexHtml writer.
Merge branch 'master' into doc-tags
Add --css option.

To include additional CSS to the page.
The CSS will get appended to the CSS generated by Tag classes.
Make --css, --head-html, --body-html accept filename.

Useful for reading in larger chunks of HTML or CSS.
Avoid :param_count warning for case of varargs.

When using variable number of arguments it's common that the
arguments are read from `arguments` array instead of the actual
parameter variables.
Allow passing file & linenr to Logger#warn as hash.

Getting rid of lots of code scattered around all over that deals
with extracting the filename and linenr out of some hash and
passing them as separate arguments.
Pass file and line as single param in Doc::Parser.

Not much of a change, but at least one less instance variable.
Typo in enum warning type doc.
Add position paramater to Tag#parse_doc.

This will now break all the extensions written so far against 5.0 beta.
However, I think it's only right to provide the position information
also inside #parse_doc allowing therefore warnings to be reported
in that stage too.  And it's the right time to make this change.