Removing specific versions from requirements (#504)

requirements-dev.txt

-future>=0.16.0
-requests>=2.9.1
-paramiko>=1.16.0
-pysnmp>=4.3.2
-pycryptodome==3.6.6
-pytest==3.5.1
-pytest-forked==0.2
-pytest-xdist==1.22.2
-flake8==3.5.0
+future
+requests
+paramiko
+pysnmp
+pycryptodome
+pytest
+pytest-forked
+pytest-xdist
+flake8
 git+git://github.com/threat9/threat9-test-bed

requirements.txt

-future>=0.16.0
-requests>=2.9.1
-paramiko>=1.16.0
-pysnmp>=4.3.2
-pycryptodome==3.6.6
+future
+requests
+paramiko
+pysnmp
+pycryptodome