Update dependencies

setup.py

@@ -5,15 +5,15 @@
 
 setuptools.setup(
     name="marlin_binary_protocol",
-    version="0.0.6",
+    version="0.0.7",
     author="Charles Willis",
     author_email="[email protected]",
     description="Transfer files with Marlin 2.0 firmware using Marlin Binary Protocol Mark II",
     long_description=long_description,
     long_description_content_type="text/markdown",
     url="https://github.com/charleswillis3/marlin-binary-protocol",
     packages=setuptools.find_packages(),
-    install_requires=["heatshrink>=0.3.2", "heatshrink2>=0.9", "pyserial>=3.4"],
+    install_requires=["heatshrink>=0.3.2", "heatshrink2>=0.9", "pyserial>=3.4", "backports.time_perf_counter; python_version < '3.3'"],
     classifiers=[
         "Programming Language :: Python :: 2.7",
         "Programming Language :: Python :: 3",