server/general: ditch falcon for in-house WSGI app

For quite some time, I hated Falcon's class maps approach that caused
more chaos than good for Szurubooru. I've taken a look at the other
frameworks (hug, flask, etc) again, but they all looked too
bloated/over-engineered. I decided to just talk to WSGI myself.

Regex-based routing may not be the fastest in the world, but I'm fine
with response time of 10 ms for cached /posts.

server/requirements.txt

@@ -1,6 +1,5 @@
 alembic>=0.8.5
 pyyaml>=3.11
-falcon>=0.3.0
 psycopg2>=2.6.1
 SQLAlchemy>=1.0.12
 pytest>=2.9.1