Automatically refresh error list after syntax check
Improve naming of error display functions
Remove function to display errors in list

The error list is going to highlight the error at point automatically
now, so this function becomes superfluous.  I doesn't play well with
auto-refreshing error lists anyway.
Highlight errors at point in the error list
Refresh the error list when clearing Flycheck state
Update the changelog
Automatically recenter the error list at highlighted errors
Remove broken test cases

As the behavior of the error list greatly changed, these test cases are
broken.  We need new ones.
Simplify restoring of the selected window
Use the real error list source buffer when refreshing
Refactor error list source management
Automatically update error list when switching buffers
Update documentation of the error list
Simplify re-centering

Do calculations with point positions instead of line numbers
Fix highlighting of first error in the list

The error list has no header anymore, so we don't need to account for it
by a one line offset from the buffer beginning.
Add flycheck-cask to the manual
Update extension URLs
Update Cask URLs and remove all Carton references
Credit @tom-tan for his extension
Highlight and synchronize errors list dynamically on post-command-hook.