Merge pull request #10 from jibbius/master

Allow user to specify which fields get exported (+ 2 others)
Attempting to fix Travis test runner

Removed deprecated WordPress and Gravity Forms versions
Formatting and pass tests

Fixed formatting for previous contributor commits. Fixed failing tests
due to new commits and PHPMailer behavior changes.
Changed screenshot

Reflecting the new functionality
Version bump

Bumped to 0.3.0 since we broke some of the backcompatiblity.
Awaiting tests for new features and then we can do a release on 0.3.1