heroku: adding settings.py file used in heroku

.gitignore

@@ -4,7 +4,6 @@
 
 /TODO.txt
 /dist
-/settings.py
 /src/relengapi/.coverage
 /src/relengapi/.coverage-html
 /src/relengapi/docs_build_dir/

settings.py

@@ -0,0 +1,11 @@
+import os
+
+SQLALCHEMY_DATABASE_URI = os.environ.get('SQLALCHEMY_DATABASE_URI')
+
+if not SQLALCHEMY_DATABASE_URI:
+    raise Exception("You need to specify SQLALCHEMY_DATABASE_URI variable.")
+
+SQLALCHEMY_TRACK_MODIFICATIONS = False
+SQLALCHEMY_DATABASE_URIS = dict(
+    clobberer=SQLALCHEMY_DATABASE_URI,
+)