CloudTrails service support

[fpiche]

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Development documentation
and specifically the Pull Request Guidelines.

IMPORTANT: Please take note of the below checklist, especially the first three items.

Summary

Added support for CloudTrails service

Pull Request Checklist

• All pull requests should be against the develop branch, not master.
• All pull requests must include the Contributor License Agreement (see below).
• Whether or not your PR includes unit tests:
  • Please make sure you have run the exact code contained in the PR locally, and it functions as desired.
  • Please make sure the TravisCI build passes or, if not, you've corrected any obvious problems identified by the tests.
• Code should conform to the Development Guidelines:
  • pep8 compliant with some exceptions (see pytest.ini)
  • 100% test coverage with pytest (with valid tests). If you have difficulty
    writing tests for the code, that's fine, just mention that in the summary and either
    ask for assistance, or clarify that you'd like someone else to handle the tests. PRs that
    include complete test coverage will usually be merged faster.
  • Complete, correctly-formatted documentation for all classes, functions and methods.
  • documentation has been rebuilt with tox -e docs
  • Connections to the AWS services should only be made by the class's
    connect() and connect_resource() methods, inherited from
    awslimitchecker.connectable.Connectable
  • All modules should have (and use) module-level loggers.
  • Commit messages should be meaningful, and reference the Issue number
    if you're working on a GitHub issue (i.e. "issue #x - "). Please
    refrain from using the "fixes #x" notation unless you are sure that the
    the issue is fixed in that commit.
  • Git history is fully intact; please do not squash or rewrite history.

Contributor License Agreement

By submitting this work for inclusion in awslimitchecker, I agree to the following terms:

• The contribution included in this request (and any subsequent revisions or versions of it)
  is being made under the same license as the awslimitchecker project (the Affero GPL v3,
  or any subsequent version of that license if adopted by awslimitchecker).
• My contribution may perpetually be included in and distributed with awslimitchecker; submitting
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  under the terms of awslimitchecker's license.
• I have the legal power and rights to agree to these terms.

[codecov-io]

Codecov Report

Merging #350 into develop will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           develop   #350   +/-   ##
======================================
  Coverage      100%   100%           
======================================
  Files           28     29    +1     
  Lines         2107   2148   +41     
  Branches       318    322    +4     
======================================
+ Hits          2107   2148   +41

Impacted Files	Coverage Δ
awslimitchecker/services/cloudtrail.py	100% <100%> (ø)

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[jantman]

This was released in 5.0.0 just now, and should be live on PyPI.