Fixed flipped seismic cmap

- fixed cmap `seismic` mistakenly drawn from red (negative) to blue
  (positive) instead of its supposed order from blue (negative) to red
  (positive)
- fixed comment for cmap `france` to *blue to red* (was *red to blue*)

zennit/image.py

@@ -38,10 +38,10 @@
     'coldnhot': '0ff,00f,80:000,f00,ff0,fff',
     # combination of wblue (reversed) and wred, centered around white
     'bwr': '00f,80:fff,f00',
-    # red to white to blue as in the french flag
+    # blue to white to red as in the french flag
     'france': '0055a4,80:fff,ef4135',
-    # red to white to blue with brightness 0xd0
-    'seismic': 'd00000,80:d0d0d0,0000d0',
+    # blue to white to red with brightness 0xd0
+    'seismic': '0000d0,80:d0d0d0,d00000',
     # cyan to white to magenta with brightness 0xd0
     'coolio': '00d0d0,80:d0d0d0,d000d0',
     # green to white to magenta with brightness 0xd0