Revert "ENH: Adds license message on first import"

[miykael]

Tests on TravisCI were failing because of the license check introduced with PR #71. This was the case for general tests (https://travis-ci.org/miykael/atlasreader/jobs/476838506) as well as for tests in the notebook (https://travis-ci.org/miykael/atlasreader/jobs/476838507).

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@6a7ec04). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master      #86   +/-   ##
=========================================
  Coverage          ?   87.87%           
=========================================
  Files             ?        6           
  Lines             ?      396           
  Branches          ?        0           
=========================================
  Hits              ?      348           
  Misses            ?       48           
  Partials          ?        0

Impacted Files	Coverage Δ
atlasreader/__init__.py	100% <ø> (ø)
atlasreader/tests/test_cli.py	100% <100%> (ø)

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