1.15 release preparations

- Update texture error string
- Update docs
- Add missing newline at the end of textures.py

docs/running.rst

@@ -273,14 +273,14 @@ If you want or need to provide your own textures, you have several options:
 
   ::
 
-    VERSION=1.14
+    VERSION=1.15
     mkdir -p ~/.minecraft/versions/${VERSION}/
     wget https://overviewer.org/textures/${VERSION} -O ~/.minecraft/versions/${VERSION}/${VERSION}.jar
 
   If that's too confusing for you, then just take this single line and paste it into
   a terminal to get 1.14 textures::
 
-    wget https://overviewer.org/textures/1.14 -O ~/.minecraft/versions/1.14/1.14.jar
+    wget https://overviewer.org/textures/1.15 -O ~/.minecraft/versions/1.15/1.15.jar
 
 * You can also just run the launcher to install the client.