Screw it; go 3.7 for ``datetime.fromisoformat()``

.travis.yml

@@ -1,10 +1,10 @@
 language: python
-python:
-    - '3.6'
-    # setup.py reading README breaks this?
-    # - pypy
-    # no pandas support
-    # - nightly
+
+matrix:
+    include:
+        - python: 3.7
+          dist: xenial
+          sudo: required
 
 before_install:
     - sudo apt-get -qq update

setup.py

@@ -43,7 +43,7 @@ setup(
         'questrade': ['asks'],
     },
     tests_require=['pytest'],
-    python_requires=">=3.6",
+    python_requires=">=3.7",  # literally for ``datetime.datetime.fromisoformat``...
     keywords=["async", "trading", "finance", "quant", "charting"],
     classifiers=[
         'Development Status :: 3 - Alpha',