Check for _mini

In the editor.Editor.set_tab_usage definition, the code would check to see if self._mini evaluates to True.  This was a problem if self._mini had not been created yet, such as when opening a new file.  As I'm working on a Go project right now and don't feel like switching editors for it, I had to fix that in order to be able to open files in that project - because Go's style guide recommends tabs (and, in fact, gofmt converts spaces to tabs).
Added missing attr initialization (ConsoleWidget.history_index).
Without this initialization if the user press UP/Down keys and there the
ConsoleWidget._history still empty the ConsoleWidget fail until the user enter some command.
Merge branch 'console_history_index'
clean up pep8 violations.
remove pep8 violations
take out pep8 violations.
take out pep8 violations
take out pep8 violations
take out pep8 violations
take out pep8 violations
take out pep8 violations
take out pep8 violations
take out pep8 violations.
take out pep8 violations.
take out pep8 violations.
take out pep8 violations
take out pep8 violations
take out pep8 violations.
take pep8 violations
take out pep8 violations