wmforecast.c: Move default colors to #defines.
Remove autotools-generated files.
.gitignore: Add auto-generated files previously under version control.
configure.ac: Remove AC_SUBST(VERSION); unnecessary.
wmforecast.c: Use PACKAGE_STRING for --version; update to reflect GNU coding
standards (http://www.gnu.org/prep/standards/html_node/_002d_002dversion.html).
wmforecast.c: Print -help text when invalid command line option given.
wmforecast.c: Simplify --help output, add homepage.
wmforecast.c: Add command line options to set colors.

In particular, -b or --background can be used to set the background color
and -t or --text can be used to set the text color.  These can also be set
in ~/.config/wmforecast/wmforecastrc by setting "background" and "text",
respectively.
wmforecast.c: Add new colors to preferences GUI (still in progress!)