Move requests to install_requires (opensearch-project#142)

Signed-off-by: Sam Foster <sfoster.ka@gmail.com>

Author: sfoster3

setup.py

@@ -51,6 +51,7 @@
 install_requires = [
     "urllib3>=1.21.1, <2",
     "certifi",
+    "requests>=2.4.0, <3.0.0",
 ]
 tests_require = [
     "requests>=2.0.0, <3.0.0",
@@ -112,7 +113,6 @@
     extras_require={
         "develop": tests_require + docs_require + generate_require,
         "docs": docs_require,
-        "requests": ["requests>=2.4.0, <3.0.0"],
         "async": async_require,
     },
 )