MNT remove requirements files and move it in setup.py (#816)

Author: glemaitre

doc/whats_new/v0.8.rst

@@ -51,6 +51,13 @@ Bug fixes
   even with `validate=False` when calling `fit`.
   :pr:`790` by :user:`Guillaume Lemaitre <glemaitre>`.
 
+Maintenance
+...........
+
+- Remove requirements files in favour of adding the packages in the
+  `extras_require` within the `setup.py` file.
+  :pr:`816` by :user:`Guillaume Lemaitre <glemaitre>`.
+
 Deprecation
 ...........
 

requirements.dev.txt

@@ -45,7 +45,18 @@
     "joblib>=0.11",
 ]
 EXTRAS_REQUIRE = {
-    "tests": ["pytest", "pytest-cov"],
+    "optional": [
+        "keras",
+        "tensorflow",
+    ],
+    "dev": [
+        "black",
+        "flake8",
+    ],
+    "tests": [
+        "pytest",
+        "pytest-cov",
+    ],
     "docs": [
         "sphinx",
         "sphinx-gallery",