Improve tests/CI configuration

- Add Python 3.10
- Fix DeprecationWarning for pytest and --strict option
- Install typing for Python 3.4
- Allow passing arguments to pytest command in tox

.travis.yml

@@ -7,7 +7,8 @@ python:
 - 3.6
 - 3.7
 - 3.8
-- 3.9-dev
+- 3.9
+- 3.10-dev
 - pypy2.7-6.0
 - pypy3.5
 

tox.ini

@@ -6,7 +6,7 @@ envlist =
     flake8
     pylint
     bandit
-    py{27,34,35,36,37,38,39,py,py3}
+    py{27,34,35,36,37,38,39,310,py,py3}
     readme
     requirements
     clean
@@ -15,7 +15,8 @@ envlist =
 description = Unit tests
 deps =
     pytest
-commands = pytest
+    py34: typing
+commands = pytest {posargs}
 
 [testenv:bandit]
 description = PyCQA security linter
@@ -58,4 +59,4 @@ targets = .
 exclude = .tox,build,dist,pysnooper.egg-info
 
 [pytest]
-addopts = --strict
+addopts = --strict-markers