allow bytes-like for key/iv/data for symmetric encryption (#4621)

* allow bytearrays for key/iv for symmetric encryption

* bump pypy/cffi requirements

* update docs, fix some tests

* old openssl is naught but pain

* revert a typo

* use trusty for old pypy

* better error msg again

* restore match
diff --git a/setup.py b/setup.py
index bd98fd5..5b29d32 100644
--- a/setup.py
+++ b/setup.py
@@ -44,12 +44,12 @@
 VECTORS_DEPENDENCY = "cryptography_vectors=={0}".format(about['__version__'])
 
 # `setup_requirements` must be kept in sync with `pyproject.toml`
-setup_requirements = ["cffi>=1.7,!=1.11.3"]
+setup_requirements = ["cffi>=1.8,!=1.11.3"]
 
 if platform.python_implementation() == "PyPy":
-    if sys.pypy_version_info < (5, 3):
+    if sys.pypy_version_info < (5, 4):
         raise RuntimeError(
-            "cryptography is not compatible with PyPy < 5.3. Please upgrade "
+            "cryptography is not compatible with PyPy < 5.4. Please upgrade "
             "PyPy to use this library."
         )