Changes:
  [0.5.1] (20171021)
   - Fix #3 (Unicode issue when exporting).
   - New donations section in about tab.
  [0.5.0] (20170420)
   - New buttons to export and import AutoFields to/from JSON files.
   - Context menu in 'List of AutoFields' tab to assing a disabled AutoField to
     another layer.
  [0.4.0] (20160909)
   - New option to calculate the expression on existing features.
  [0.3.0] (20160817)
   - Official release!
   - AutoFieldManager: normalize sources from 'Add PostgreSQL layer' and
     DBManager so that they coincide.
   - AutoFieldManager: Make createAutoFields return the autoFieldId on success,
     as it can be used later to remove the AutoField via removeAutoField.
   - GUI: Layer list now listens to Layer Tree SIGNALs to keep itself updated.
   - Added link to documentation from About tab. It's aware of language [en|es].
  [0.2.7] (20160804)
   - Implement order for AutoFields storage and for setting event connections,
     so that scenarios of AutoFields depending on other AutoFields become
     predictable.
   - EventManager: Change str() by unicode() in a debug message that was
     causing a Python error if values calculated contained non-ascii characters.
   - Adjusted plugin description in all Python files.
  [0.2.6] (20160802)
   - GUI: Add checkbox to filter (only show enabled AutoFields) the list of
     AutoFields.
   - Event Manager: If an expression has parse or eval errors, None is passed
     as result to changeAttributeValue, which is stored by QGIS as NULL. This
     fixes a bug that happened returning False from aforementioned errors.
   - Hide Redo buttons and keyboard shortcut from QGIS GUI because it can lead
     to QGIS crashes due to corrupted undo stack.
   - Small fix in removeAutoField. Check that autoFieldId to remove exists.
  [0.2.5] (20160726)
   - Added support for translations. Added Spanish translation.
   - Added support for getting area and distance units in calculations from
     QGIS preferences (QGIS v.>=2.14).
   - Expression Dialog: Added support for QGIS variables and recent expressions.
   - The plugin now deals with Adding/Removing fields in an edit session.
   - Message with button to let users know they should save edits for
     calculating AutoFields when adding new features.
  [0.2.4] (20160722)
   - Opening Custom Expression window for a field that is already an AutoField
     brings the stored expression making it possible to modify it.
   - Fix for problem on Windows regarding different path separators in public
     sources when opening the same layer from 'Add Layer' and QGIS browser.
  [0.2.3] (20160720)
   - Overwriting an AutoField is now possible.
   - Fixed issue with QGIS locale and provider capabilities (Thanks Thomas B.!)
   - Fixed issue with removing multiple layers from QGIS ToC.
  [0.2.2] (20160718)
   - Workaround for QGIS crash due to bug #15311 Instead of featureAdded, use
     committedFeatureAdded SIGNAL for all expressions.
  [0.2.1] (20160717)
   - Fix for expressions that work when new features are saved to provider
     (e.g., $id).
   - Fix for convertCompatible, as the Python API returns QVariant, not bool as
     C++.
  [0.2] (20160714)
   - Ready for testing.
  [0.1] (20160707)
   - First working GUI version
  [0] (20160522) It all started...
