unable to open playlist containing quoted URIs
Hi there,

When trying to  open `http://bassdrive.com/v2/streams/BassDrive.pls`, mopidy fails with:

```
 GStreamer-CRITICAL **: 05:00:20.205: gst_element_make_from_uri: assertion 'gst_uri_is_valid (uri)' failed
WARNING  Download of '"http://bassdrive.radioca.st:80"' failed due to unsupported schema
INFO     Unwrapping stream from URI (http://bassdrive.com/v2/streams/BassDrive.pls) failed: error downloading URI "http://bassdrive.radioca.st:80"
WARNING  Track is not playable: http://bassdrive.com/v2/streams/BassDrive.pls
```
Looking at the content of  `http://bassdrive.com/v2/streams/BassDrive.pls` I can see that the FileX entries (the URIs) are quoted:
```
[playlist]
numberofentries=10
File1="http://bassdrive.radioca.st:80"
Title1="(#1) Bassdrive - Worldwide Drum and Bass Radio"
Length1=-1
...
```
I have tried the following hack and it seems to work for me, confirming that the issue is in the decoding:
```
diff --git a/mopidy/stream/actor.py b/mopidy/stream/actor.py
index 1bdd05ca..a4ab36b1 100644
--- a/mopidy/stream/actor.py
+++ b/mopidy/stream/actor.py
@@ -160,4 +160,4 @@ def _unwrap_stream(uri, timeout, scanner, requests_session):
         # TODO Test streams and return first that seems to be playable
         logger.debug(
             'Parsed playlist (%s) and found new URI: %s', uri, uris[0])
-        uri = uris[0]
+        uri = uris[0].strip('\\"')
```
Let me know if you want me to create a PR with this fix if it is deemed appropriate enough, and I'll try to add a test case.

Cheers,
Gildas
diff --git a/mopidy/internal/playlists.py b/mopidy/internal/playlists.py
index 5c7c8fc4..59c28d4b 100644
--- a/mopidy/internal/playlists.py
+++ b/mopidy/internal/playlists.py
@@ -84,7 +84,7 @@ def parse_pls(data):
         if section.lower() != 'playlist':
             continue
         for i in range(cp.getint(section, 'numberofentries')):
-            yield cp.get(section, 'file%d' % (i + 1))
+            yield cp.get(section, 'file%d' % (i + 1)).strip('\\"\\'')
 
 
 def parse_xspf(data):
diff --git a/tests/internal/test_playlists.py b/tests/internal/test_playlists.py
index 9a1c49d5..1abbf57c 100644
--- a/tests/internal/test_playlists.py
+++ b/tests/internal/test_playlists.py
@@ -31,11 +31,11 @@ file:///tmp/baz
 
 PLS = b"""[Playlist]
 NumberOfEntries=3
-File1=file:///tmp/foo
+File1="file:///tmp/foo"
 Title1=Sample Title
 Length1=123
 
-File2=file:///tmp/bar
+File2='file:///tmp/bar'
 Title2=Example \\xc5\\xa7\\xc5\\x95
 Length2=321
 File3=file:///tmp/baz
['mopidy/internal/playlists.py', 'tests/internal/test_playlists.py']