Changed variables to protected

It would be nice to have variables as protected, to inherit class
merged branch yosmanyga/patch-1 (PR #181)

This PR was submitted for the 2.0 branch but it was merged into the 2.1 branch instead (closes #181).

Discussion
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Changed variables to protected

It would be nice to have variables as protected, to inherit class.

Commits
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edf2e00 Changed variables to protected
Doc typo fixed -no-interaction
merged branch carlossg00/master (PR #180)

This PR was submitted for the master branch but it was merged into the 2.1 branch instead (closes #180).

Discussion
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Fixed doc typo, --no-interaction instead of --non-interaction

Commits
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4836211 Doc typo fixed -no-interaction
Fixed build error 'WARNING: document isn't included in any toctree'
merged branch WouterJ/patch-3 (PR #185)

This PR was merged into the 2.1 branch.

Discussion
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Fixed build error 'WARNING: document isn't included in any toctree'

this should get merged into 2.2 and master aswell, I don't know if this is done automatically in this repo.

Commits
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fa3c528 Fixed build error 'WARNING: document isn't included in any toctree'
Merge branch '2.1' into 2.2

* 2.1:
  Fixed build error 'WARNING: document isn't included in any toctree'
  Doc typo fixed -no-interaction
  Changed variables to protected