📌 Loosen Pipfile requirements

See also: tmux-python/tmuxp@2e01c32

Author: tony

Pipfile

@@ -4,13 +4,14 @@ verify_ssl = true
 name = "pypi"
 
 [dev-packages]
-alagitpull = ">=0.0.21"
+alagitpull = "*"
 Sphinx = ">=2.0.0"
-flake8 = "==3.7.7"
-isort = "==4.3.18"
-pytest = "==4.5.0"
-pytest-mock = "==1.10.4"
+flake8 = "*"
+isort = "*"
+pytest = "*"
+pytest-mock = "*"
 libvcs = {path = ".",editable = true}
+black = "==19.3b0"
 
 [packages]