set upper version constraint for dependencies to prevent unexpected breaking changes

https://semver.org/#spec-item-8

Pipfile

@@ -7,10 +7,10 @@ name = "pypi"
 freesurfer-volume-reader = {editable = true, path = "."}
 
 [dev-packages]
-pylint = ">=2.3.0"
+pylint = ">=2.3.0,<3"
-pytest = "*"
+pytest = "<5"
 pytest-cov = "<3,>=2"
-pytest-timeout = "*"
+pytest-timeout = "<2"
 
 [requires]
 python_version = "3"

Pipfile.lock

@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "a697197be3cbcb744df6e058a1d4f70ecbb0c81821ca98d6e29b111119816171"
+            "sha256": "1098dcb0de047a6726ac1f5e983fd9b6121133064140378c7a0fdba064a7d10f"
         },
         "pipfile-spec": 6,
         "requires": {

setup.py

@@ -41,15 +41,15 @@ setuptools.setup(
     },
     install_requires=[
         # pandas.DataFrame.drop(columns=[...], ...)
-        'pandas>=0.21.0',
+        'pandas>=0.21.0,<1',
     ],
     setup_requires=[
         'setuptools_scm',
     ],
     tests_require=[
-        'pylint>=2.3.0',
+        'pylint>=2.3.0,<3',
-        'pytest',
+        'pytest<5',
         'pytest-cov<3,>=2',
-        'pytest-timeout',
+        'pytest-timeout<2',
     ],
 )