Fix #22 Python 3.4 compatibility

[tterb]

Description

Removed unnecessary import to fix issues with Python 3.4 compatibility

Motivation and Context

Fixes #22

How Has This Been Tested?

Tested in Python 3.4-3.7 with python setup.py test

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING.md document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov-io]

Codecov Report

Merging #26 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #26      +/-   ##
==========================================
- Coverage   94.78%   94.76%   -0.02%     
==========================================
  Files           4        4              
  Lines         230      229       -1     
==========================================
- Hits          218      217       -1     
  Misses         12       12