Use an instance of whatever the old interpreter was
don't hardcode prompts
factor out checking if buffer could be complete and is valid
import completion uses less local functions (more testable!)
split up process_event
remove unused property
all update_completion calls implicit on set current line / cursor
cleaned up process_event more
improve imports
format init of Repl more nicely
Merge branch 'innocuous-changes-for-monkeypatching' into process-event-refactor

Conflicts:
	bpython/curtsiesfrontend/repl.py
Fix stopping watching modules with errors

Also watch files that had errors in them that have been successfully
imported before
fix #349

introduces inconsistent coloring (last line of stderr will not be red,
rest still will be) but this will be fixed soon by explicit traceback +
error syntax highlighting.
fix #332
fix #342 import completion regression
Merge branch 'process-event-refactor'
more process_event refactoring