Drop support for python3.5

CI fails on datetime tests for timezone offsets with seconds
only on python3.5. There's no obvious cause for version differences
in the CPython datetime FFI API docs.

Author: ijl

.travis.yml

@@ -3,7 +3,6 @@ dist: xenial
 language: python
 
 python:
-  - "3.5"
   - "3.6"
   - "3.7"
 

Cargo.toml

@@ -24,7 +24,6 @@ classifier = [
     "Operating System :: MacOS",
     "Operating System :: POSIX :: Linux",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.5",
     "Programming Language :: Python :: 3.6",
     "Programming Language :: Python :: 3.7",
     "Programming Language :: Python",

README.md

@@ -6,7 +6,7 @@ other library and 4.5x to 11.5x the standard library. Its deserialization
 performance is 1.05x to 1.2x the nearest other library and 1.2x to 4x
 the standard library.
 
-It supports CPython 3.5, 3.6, and 3.7. Its API is a subset of the
+It supports CPython 3.6 and 3.7. Its API is a subset of the
 API of the standard library's json module.
 
 ## Usage

test/test_jsonchecker.py

@@ -237,7 +237,6 @@ def test_fail33(self):
         """
         self._run_fail_json('fail33.json')
 
-    @unittest.skipIf(sys.version_info < (3, 6), "Indeterminate key order")
     def test_pass01(self):
         """
         pass01.json
@@ -256,7 +255,6 @@ def test_pass02(self):
             b'[[[[[[[[[[[[[[[[[[["Not too deep"]]]]]]]]]]]]]]]]]]]'
         )
 
-    @unittest.skipIf(sys.version_info < (3, 6), "Indeterminate key order")
     def test_pass03(self):
         """
         pass03.json

test/test_roundtrip.py

@@ -75,7 +75,6 @@ def test_roundtrip009(self):
         """
         self._run_roundtrip_json('roundtrip09.json')
 
-    @unittest.skipIf(sys.version_info < (3, 6), "Indeterminate key order")
     def test_roundtrip010(self):
         """
         roundtrip010.json

test/test_ujson.py

@@ -346,14 +346,12 @@ def test_decodeNullCharacter(self):
         input = "\"31337 \\u0000 31337\""
         self.assertEqual(orjson.loads(input), json.loads(input))
 
-    @unittest.skipIf(sys.version_info < (3, 6), "Bytes input not supported in older Python versions")
     def test_decodeEscape(self):
         base = '\u00e5'.encode('utf-8')
         quote = "\"".encode()
         input = quote + base + quote
         self.assertEqual(json.loads(input), orjson.loads(input))
 
-    @unittest.skipIf(sys.version_info < (3, 6), "Bytes input not supported in older Python versions")
     def test_decodeBigEscape(self):
         for _ in range(10):
             base = '\u00e5'.encode('utf-8')