ToolBar: Listen to Action name changes for toolbar actions.

Checkable actions especially change their name in response to
checked state change, toolbar buttons now honor the change in
the action's name and change the button text accordingly.
Update EnamlTaskPane to enaml 0.8.8 .
Update EnamlDockPane to Enaml 0.8.8 .
Update EnamlEditor to Enaml 0.8.8 .
Remove redundancies from EnamlTaskPane and EnamlEditor.
Small cleanups.
Add requirements for developers.

These are requirements for development tasks, as for example
running the tests.
Request relayout only if Enaml component supports it.
Reset the 'component' traits in the enaml panes after destruction.
Make enaml imports lazy.

This is to avoid that imports from pyface.tasks.api import enaml,
which is 1) undesirable and 2) breaks Canopy if it finds the new
PyFace while using the old Enaml.
Update the enaml-based example.
Merge pull request #92 from enthought/enaml-0.8-migration

Enaml 0.8 migration
Bump version number.
Add change log file with brief summary of 4.4.0 changes.
Bump copyright dates.
Added details in CHANGES.txt.
Merge pull request #93 from enthought/release/4.4.0

4.4.0 Release
add links to the online documentation to the README file so the docs can be found
rerun sphinx-apidoc
Change advanced editor area tab switching shortcut to Ctrl+PgUp/Down.

This is a common shortcut used which works in many applications
such as google chrome and firefox.