Added pip-tools and upgraded dependencies

requirements.in

@@ -0,0 +1,8 @@
+py>=1.7.0
+pytest>=4.0.2
+PyYAML>=3.13
+requests>=2.20.0
+responses>=0.10.5
+tweepy>=3.7.0
+
+

requirements.txt

@@ -1,19 +1,24 @@
-attrs==18.1.0
-certifi==2018.4.16
-chardet==3.0.4
-cookies==2.2.1
-idna==2.6
-issue==0.1.5
-more-itertools==4.1.0
-oauthlib==2.0.7
-pluggy==0.6.0
-py==1.5.3
-PySocks==1.6.8
-pytest==3.5.1
-PyYAML==3.12
-requests==2.18.4
-requests-oauthlib==0.8.0
-responses==0.9.0
-six==1.11.0
-tweepy==3.6.0
-urllib3==1.22
+#
+# This file is autogenerated by pip-compile
+# To update, run:
+#
+#    pip-compile --output-file requirements.txt requirements.in
+#
+atomicwrites==1.2.1       # via pytest
+attrs==18.2.0             # via pytest
+certifi==2018.11.29       # via requests
+chardet==3.0.4            # via requests
+idna==2.8                 # via requests
+more-itertools==4.3.0     # via pytest
+oauthlib==2.1.0           # via requests-oauthlib
+pluggy==0.8.0             # via pytest
+py==1.7.0
+pysocks==1.6.8            # via tweepy
+pytest==4.0.2
+pyyaml==3.13
+requests-oauthlib==1.0.0  # via tweepy
+requests==2.21.0
+responses==0.10.5
+six==1.12.0               # via more-itertools, pytest, responses, tweepy
+tweepy==3.7.0
+urllib3==1.24.1           # via requests