Pin SQLAlchemy to 1.1.15 for now

Until I fix the 'StaleDataError' error.

requirements.txt

@@ -44,7 +44,7 @@ requests==2.18.4
 simplejson==3.13.2
 six==1.11.0
 speaklater==1.3
-SQLAlchemy==1.2.2
+SQLAlchemy==1.1.15
 SQLAlchemy-Utils==0.32.21
 Unidecode==1.0.22
 urllib3==1.22