Keep all torrent files and poster images in app config folder

Fixes #402

renderer/lib/torrent-poster.js

@@ -20,7 +20,7 @@ function torrentPoster (torrent, cb) {
 
 function getLargestFileByExtension (torrent, extensions) {
   var files = torrent.files.filter(function (file) {
-    var extname = path.extname(file.name)
+    var extname = path.extname(file.name).toLowerCase()
     return extensions.indexOf(extname) !== -1
   })
   if (files.length === 0) return undefined

renderer/lib/torrent-summary.js

@@ -0,0 +1,24 @@
+module.exports = {
+  getPosterPath,
+  getTorrentPath
+}
+
+var path = require('path')
+var config = require('../../config')
+
+// Expects a torrentSummary
+// Returns an absolute path to the torrent file, or null if unavailable
+function getTorrentPath (torrentSummary) {
+  if (!torrentSummary || !torrentSummary.torrentFileName) return null
+  return path.join(config.CONFIG_TORRENT_PATH, torrentSummary.torrentFileName)
+}
+
+// Expects a torrentSummary
+// Returns an absolute path to the poster image, or null if unavailable
+function getPosterPath (torrentSummary) {
+  if (!torrentSummary || !torrentSummary.posterFileName) return null
+  var posterPath = path.join(config.CONFIG_POSTER_PATH, torrentSummary.posterFileName)
+  // Work around a Chrome bug (reproduced in vanilla Chrome, not just Electron):
+  // Backslashes in URLS in CSS cause bizarre string encoding issues
+  return posterPath.replace(/\\/g, '/')
+}