Treat message.body as UTF-8 in RouteValidator

After updating lita from v3.2.0 to v3.3.0, I got `Encoding::CompatibilityError` with ShellAdapter.
So, I tried to fix it.

Here is my chatbot repository:  [fukayatsu/twitter-fkbot at lita-v330](https://github.com/fukayatsu/twitter-fkbot/tree/lita-v330)

```
fk82% lita
Type "exit" or "quit" to end the session.
lita > lita img me sushi
http://www.zippys.com/wp-content/uploads/2013/02/SushiPlatter-web.jpg
lita > lita 寿司
/Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/route_validator.rb:50:in `===': incompatible encoding regexp match (UTF-8 regexp with ASCII-8BIT string) (Encoding::CompatibilityError)
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/route_validator.rb:50:in `matches_pattern?'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/route_validator.rb:29:in `call'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/handler.rb:166:in `route_applies?'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/handler.rb:65:in `block in dispatch'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/handler.rb:64:in `each'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/handler.rb:64:in `dispatch'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/robot.rb:39:in `block in receive'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/2.1.0/set.rb:263:in `each_key'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/2.1.0/set.rb:263:in `each'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/robot.rb:39:in `receive'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/adapters/shell.rb:70:in `block in run_loop'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/adapters/shell.rb:61:in `loop'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/adapters/shell.rb:61:in `run_loop'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/adapters/shell.rb:15:in `run'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/robot.rb:47:in `run'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita.rb:141:in `run'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/lib/lita/cli.rb:75:in `start'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/thor-0.19.1/lib/thor/command.rb:27:in `run'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/thor-0.19.1/lib/thor/invocation.rb:126:in `invoke_command'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/thor-0.19.1/lib/thor.rb:359:in `dispatch'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/thor-0.19.1/lib/thor/base.rb:440:in `start'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/lita-3.3.0/bin/lita:6:in `<top (required)>'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/bin/lita:23:in `load'
	from /Users/fukayatsu/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/bin/lita:23:in `<main>'
```