Set default Encoding to UTF_8 for Ruby 1.9

[darthdeus]

Running rake convert_bundles on Ruby 1.9 will cause invalid byte sequence in US-ASCII exception.

Converting from extras/bundles/html-tmbundle
./extras/textmate_import.rb -d extras/bundles/html-tmbundle -o ./extras/imported/html-mode -q
./extras/textmate_import.rb:362:in `split': invalid byte sequence in US-ASCII (ArgumentError)
from ./extras/textmate_import.rb:362:in `block in <main>'
from ./extras/textmate_import.rb:360:in `open'
from ./extras/textmate_import.rb:360:in `<main>'
rake aborted!
Command failed with status (1): [./extras/textmate_import.rb -d extras/bund...]

This is because Ruby 1.9 isn't reading files in UTF-8 by default and is dependent on system locale. Setting Encoding.default_external = Encoding::UTF_8 fixes the issue.

[joaotavora]

Thanks!