Bump requirements, due to security fixes in packages.

requirements.txt

@@ -5,7 +5,7 @@ cryptography==2.6.1
 distro==1.4.0
 entrypoints==0.3
 Flask==1.0.2
-httplib2==0.12.1
+httplib2>=0.18.0
 itsdangerous==1.1.0
 jeepney==0.4
 Jinja2==2.10.1
@@ -23,4 +23,4 @@ six==1.11.0
 testresources==2.0.1
 versioneer==0.18
 wadllib==1.3.3
-Werkzeug==0.15.2
+Werkzeug>=0.15.3

requirements_dev.txt

@@ -4,7 +4,7 @@ asn1crypto==0.24.0
 atomicwrites==1.3.0
 attrs==19.1.0
 Babel==2.6.0
-bleach==3.1.0
+bleach>=3.1.4
 bumpversion==0.5.3
 certifi==2019.3.9
 cffi==1.12.2
@@ -18,7 +18,7 @@ entrypoints==0.3
 filelock==3.0.10
 flake8==3.5.0
 Flask==1.0.2
-httplib2==0.12.1
+httplib2>=0.18.0
 idna==2.8
 imagesize==1.1.0
 itsdangerous==1.1.0
@@ -62,9 +62,9 @@ toml==0.10.0
 tox==3.5.2
 tqdm==4.31.1
 twine==1.12.1
-urllib3==1.24.1
+urllib3>=1.24.2
 virtualenv==16.4.3
 wadllib==1.3.3
 watchdog==0.9.0
 webencodings==0.5.1
-Werkzeug==0.15.2
+Werkzeug>=0.15.3