fix Test files appearing in distribution package #937

[slobberchops]

Description of Change

Explicitly indicated aiobotocore package as intended target for installation.

Verified that tests directory does no appear in built distribution package.

Checklist for All Submissions

• I have added change info to CHANGES.rst
• If this is resolving an issue (needed so future developers can determine if change is still necessary and under what conditions) (can be provided via link to issue with these details):
  • Detailed description of issue
  • Alternative methods considered (if any)
  • How issue is being resolved
  • How issue can be reproduced
• If this is providing a new feature (can be provided via link to issue with these details):
  • Detailed description of new feature
  • Why needed
  • Alternatives methods considered (if any)

Checklist when updating botocore and/or aiohttp versions

• I have read and followed CONTRIBUTING.rst
• I have updated test_patches.py where/if appropriate (also check if no changes necessary)
• I have ensured that the awscli/boto3 versions match the updated botocore version

[codecov]

Codecov Report

Merging #938 (4f4a128) into master (4c18d3d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #938   +/-   ##
=======================================
  Coverage   86.77%   86.77%           
=======================================
  Files          55       55           
  Lines        5295     5295           
=======================================
  Hits         4595     4595           
  Misses        700      700           

Flag	Coverage Δ
unittests	86.77% <ø> (ø)

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