Update requirements.txt

This fixes the security vulnerability, although it may break Pynome if not backwards compatible.  We're updating it anyway so shouldn't be a problem.

Author: spficklin

requirements.txt

@@ -4,6 +4,6 @@ numpy==1.14.0
 pandas==0.22.0
 pytest==3.3.1
 python-irodsclient==0.7.0
-SQLAlchemy==1.2.2
+SQLAlchemy==1.3.0
 tqdm==4.19.5
 xmltodict==0.11.0