Enable skip-non-vietnamese by default

This nice feature should be enabled by default.
Merge branch 'patch-2' of github.com:tuanta/ibus-bogo-python into develop

Conflicts:
	bogo/bogo.py
Preliminary abbreviation support
Instantiate engines ourselves so we can inject config object into them
Use setup and teardown with ibus_engine/test_engine.py
Make AbbreviationExpander accept a config object
Implement auto capitalize abbreviation feature

See test_abbreviation.py to see how it works.
Experiment with using the abbreviation expander as a simple spellchecker.
Move rules.json to data/abbr_rules.json
Remove hard dependency on an external rule file for AbbreviationExpander
Comments
Ignore a redundant error message
Refactor abbr expander
Remove dead code
Expand text after space
Refactor the auto-capitalize feature
Add a page in the config GUI for text expansion
Better error handling for text expansion