Remove py37 as circleci doesn't have it

setup.py

@@ -19,7 +19,7 @@ DESCRIPTION = "Security analysis tool for Ethereum smart contracts"
 URL = "https://github.com/ConsenSys/mythril"
 AUTHOR = "ConsenSys Dilligence"
 AUTHOR_MAIL = None
-REQUIRES_PYTHON = ">=3.5.0"
+REQUIRES_PYTHON = ">=3.6.0"
 
 
 # What packages are required for this module to be executed?
@@ -115,7 +115,6 @@ setup(
         "Intended Audience :: Science/Research",
         "Topic :: Software Development :: Disassemblers",
         "License :: OSI Approved :: MIT License",
-        "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
     ],

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py36,py37
+envlist = py36
 
 [testenv]
 deps =