Move away from gevent

Might not be that reliable

README.md

@@ -109,9 +109,6 @@ packages:
   - python3-pip
   - python3-wheels
   - python3-lxml
-  - python3-gevent
-  - python3-zope.interface
-  - python3-zope.event
   - git
   - ca-certificates
 
@@ -125,7 +122,7 @@ write_files:
 runcmd:
   - update-ca-certificates
   - pip install git+https://git.pictuga.com/pictuga/morss.git#egg=morss[full]
-  - gunicorn --bind 0.0.0.0:${PORT:-8000} --workers ${WORKERS:-4} --worker-class=gevent --preload --access-logfile - morss
+  - gunicorn --bind 0.0.0.0:${PORT:-8000} --workers ${WORKERS:-4} --threads ${THREADS:-4} --preload --access-logfile - morss
 ```
 
 ## Run
@@ -393,7 +390,8 @@ debugging.
 - `IGNORE_SSL=1`: to ignore SSL certs when fetch feeds and articles
 - `DELAY` (seconds) sets the browser cache delay, only for HTTP clients
 - `TIMEOUT` (seconds) sets the HTTP timeout when fetching rss feeds and articles
-- `WORKERS` (number) sets the number of gunicorn workers to use
+- `WORKERS` and `THREADS` (number) sets the number of gunicorn workers and
+threads to use
 
 When parsing long feeds, with a lot of items (100+), morss might take a lot of
 time to parse it, or might even run into a memory overflow on some shared