Pin versions for Pyramid and SQLAlchemy

These updates seem like they won't be trivial. I'll come back to them
soon, but I'll need to look at them more carefully and I can update
everything else in the meantime.

tildes/requirements.in

@@ -19,7 +19,7 @@ publicsuffix2==2.20160818
 pygit2
 Pygments
 pyotp
-pyramid
+pyramid<2.0
 pyramid-ipython
 pyramid-jinja2
 pyramid-session-redis==1.5.0  # 1.5.1 has a change that will invalidate current sessions
@@ -32,7 +32,7 @@ pip-tools
 redis
 requests
 sentry-sdk
-SQLAlchemy
+SQLAlchemy<1.4
 SQLAlchemy-Utils
 stripe
 titlecase