Fix JRuby incompatible encoding regexp match error

When using jRuby 1.7.16 (and 1.7.15) in Ruby 1.9 mode, we were seeing the following error when trying to access the JSON response of the future:

```
Encoding::CompatibilityError - incompatible encoding regexp match (ASCII-8BIT regexp with UTF-8 string)
```

Forcing the encoding for all regexp to use utf-8 encoding fixed the problem for us.