Update tox requirement from ~=3.6 to ~=3.14 (appium#494)

dependabot-preview[bot] · KazuCocoa · commit 4d269f828ab8 · 2020-01-27T23:14:58.000+09:00
Updates the requirements on [tox](https://github.com/tox-dev/tox) to permit the latest version. - [Release notes](https://github.com/tox-dev/tox/releases) - [Changelog](https://github.com/tox-dev/tox/blob/master/docs/changelog.rst) - [Commits](tox-dev/tox@3.6.0...3.14.3) Signed-off-by: dependabot-preview[bot] <support@dependabot.com>
diff --git a/Pipfile b/Pipfile
@@ -14,7 +14,7 @@ autopep8 = "~=1.5"
 pytest = "~=4.0"
 pytest-cov = "~=2.8"
 
-tox = "~=3.6"
+tox = "~=3.14"
 tox-travis = "~=0.12"
 
 httpretty = "~=0.9"
