Exit on ff.net error downloading chapter. Replace ':' with '_' in file name for html output, too.

ffnet.py

@@ -133,6 +133,8 @@ class FFNet(FanfictionSiteAdapter):
 			soup = None
 		div = soup.find('div', {'id' : 'storytext'})
 		if None == div:
+			logging.error("Error downloading Chapter: %s" % url)
+			exit(1)
 			return '<html/>'
 		
 		return div.prettify()

output.py

@@ -59,7 +59,7 @@ class HTMLWriter(FanficWriter):
 	
 	def __init__(self, base, name, author, inmemory=False, compress=False):
 		self.basePath = base
-		self.name = name.replace(" ", "_")
+		self.name = name.replace(" ", "_").replace(":","_")
 		self.storyTitle = name
 		self.fileName = self.basePath + '/' + self.name + '.html'
 		self.authorName = author