Character encoding

This pull request makes changes to prevent the following errors:

```ruby
/Users/Paul/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:55:in `require': /Users/Paul/.rvm/gems/ruby-1.9.3-p194/gems/jazzy-0.0.12/lib/jazzy/doc_builder.rb:92: invalid multibyte char (US-ASCII) (SyntaxError)
/Users/Paul/.rvm/gems/ruby-1.9.3-p194/gems/jazzy-0.0.12/lib/jazzy/doc_builder.rb:92: invalid multibyte char (US-ASCII)
/Users/Paul/.rvm/gems/ruby-1.9.3-p194/gems/jazzy-0.0.12/lib/jazzy/doc_builder.rb:92: syntax error, unexpected $end, expecting keyword_end
      puts 'jam out ♪♫ to your fresh new docs at ' + output_dir
                      ^
```

```ruby
/Users/Paul/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:55:in `require': /Users/Paul/.rvm/gems/ruby-1.9.3-p194/gems/jazzy-0.0.12/lib/jazzy/config.rb:46: invalid multibyte char (US-ASCII) (SyntaxError)
/Users/Paul/.rvm/gems/ruby-1.9.3-p194/gems/jazzy-0.0.12/lib/jazzy/config.rb:46: invalid multibyte char (US-ASCII)
/Users/Paul/.rvm/gems/ruby-1.9.3-p194/gems/jazzy-0.0.12/lib/jazzy/config.rb:46: syntax error, unexpected $end, expecting ')'
...odebuild-arguments arg1,arg2,…argN', Array, 'Arguments to ...
...                               ^
```

I'm not sure why these haven't been reported by anyone else.

It could be something to do with my system or version of Ruby, in which case the supported version of Ruby could be added to the Gemfile.