gensearch.rb has problems with German umlauts

[MartinThoma]

It seems to me as if your plugin cannot handle german umlauts. I think the following error is caused by an "Ä":

Generating search data for 9251 words
/home/moose/Downloads/MartinThoma.github.io/_plugins/gensearch.rb:113:in `encode': "\xC3" from ASCII-8BIT to UTF-8 (Encoding::UndefinedConversionError)
    from /home/moose/Downloads/MartinThoma.github.io/_plugins/gensearch.rb:113:in `to_json'
    from /home/moose/Downloads/MartinThoma.github.io/_plugins/gensearch.rb:113:in `generate'
    from /var/lib/gems/1.9.1/gems/jekyll-2.4.0/lib/jekyll/site.rb:251:in `block in generate'
    from /var/lib/gems/1.9.1/gems/jekyll-2.4.0/lib/jekyll/site.rb:250:in `each'
    from /var/lib/gems/1.9.1/gems/jekyll-2.4.0/lib/jekyll/site.rb:250:in `generate'
    from /var/lib/gems/1.9.1/gems/jekyll-2.4.0/lib/jekyll/site.rb:45:in `process'
    from /var/lib/gems/1.9.1/gems/jekyll-2.4.0/lib/jekyll/command.rb:28:in `process_site'
    from /var/lib/gems/1.9.1/gems/jekyll-2.4.0/lib/jekyll/commands/build.rb:55:in `build'
    from /var/lib/gems/1.9.1/gems/jekyll-2.4.0/lib/jekyll/commands/build.rb:33:in `process'
    from /var/lib/gems/1.9.1/gems/jekyll-2.4.0/lib/jekyll/commands/build.rb:17:in `block (2 levels) in init_with_program'
    from /var/lib/gems/1.9.1/gems/mercenary-0.3.4/lib/mercenary/command.rb:220:in `call'
    from /var/lib/gems/1.9.1/gems/mercenary-0.3.4/lib/mercenary/command.rb:220:in `block in execute'
    from /var/lib/gems/1.9.1/gems/mercenary-0.3.4/lib/mercenary/command.rb:220:in `each'
    from /var/lib/gems/1.9.1/gems/mercenary-0.3.4/lib/mercenary/command.rb:220:in `execute'
    from /var/lib/gems/1.9.1/gems/mercenary-0.3.4/lib/mercenary/program.rb:35:in `go'
    from /var/lib/gems/1.9.1/gems/mercenary-0.3.4/lib/mercenary.rb:22:in `program'
    from /var/lib/gems/1.9.1/gems/jekyll-2.4.0/bin/jekyll:18:in `<top (required)>'
    from /usr/local/bin/jekyll:23:in `load'
    from /usr/local/bin/jekyll:23:in `<main>'
make: *** [test] Error 1