Add support for HTML files with the htm extension as the file name for the command line interface.

When using the command line interface with the file:/   syntax.
When attempting to validate an html files that end in the extension  ".htm" the validator does not correctly recognize the file as an HTML file.

This change adds a test for the file suffix  ".htm"

/css-validator/src/org/w3c/css/css/DocumentParser.java


Around line 58 add a test for the shorter extension.

            } else if (urlLower.endsWith(".htm") ||
                       urlLower.endsWith(".html") || urlLower.endsWith(".shtml") || urlLower.endsWith("/")) {


A test for this looks like this:

java -jar css-validator.jar  -vextwarning true -profile css3 file:/C:\workspace3_4\css-validator\testdata\testhtm.htm