Add command line option for path to configuration file

Allow user to pass the path to the configuration file into the
site-generator.

site-generator

@@ -8,12 +8,13 @@
 
 	site-generator [OPTION]... PAGE|PAGE=<comma separated list of ids>...
 
-	-a, --all      generate all pages defined in configuration file
-	-l, --list     print list of configured pages
-	-p, --preview  print generated pages to standard out
-	-q, --quiet    suppress progress information while generating pages
-	-v, --verbose  print extended progress information while generating pages
-	--help         print this help message
+	-a, --all       generate all pages defined in configuration file
+	-c, --configure path to configuration file
+	-l, --list      print list of configured pages
+	-p, --preview   print generated pages to standard out
+	-q, --quiet     suppress progress information while generating pages
+	-v, --verbose   print extended progress information while generating pages
+	--help          print this help message
 
 	Where I<PAGE> is a file name of a web page 
 	or the special I<ALL> (to generate all pages).
@@ -109,15 +110,17 @@ sub main {
 
 	# Argument parsing
 	my $all;
+	my $configuration_path;
 	my $preview;
 	my $verbose;
 	my $quiet;
 	GetOptions(
-		'all'     => \$all,
-		'list'    => \&print_available_pages,
-		'preview' => \$preview,
-		'verbose' => \$verbose,
-		'quiet'   => \$quiet,
+		'all'			=> \$all,
+		'configuration=s' => \$configuration_path,
+		'list'			=> \&print_available_pages,
+		'preview'		=> \$preview,
+		'verbose'		=> \$verbose,
+		'quiet'			=> \$quiet,
 	) or pod2usage(1);
 	pod2usage(1) unless @ARGV || $all;
 	my (@page_args) = @ARGV;
@@ -126,8 +129,19 @@ sub main {
 		$verbose = 'quiet';
 	};
 
-	# Load config file
-	read_config "site.cfg" => my %config;
+	if (!$configuration_path) {
+		$configuration_path = "site.cfg";
+	}
+
+	my %config;
+	if ( -f $configuration_path ) {
+		# Load config file
+		read_config $configuration_path => %config;
+	}
+	else {
+		print STDOUT "Could not read configuration file: $configuration_path\n"; 
+		exit 1;
+	}
 
 	my $tt = get_template_html($config{DBI});