unicode characters in labels broken

[vikingosegundo]

if using unicode-strings as keys in data, they will be printed improperly to the chart

Example:

    CairoPlot.pie_plot(name='test.png', width=800, height=600, data={'eins':100, 'zwei':48, 'drei':90, 'vier':98,u'fünf':187})

the label "fünf" will be printed as "fünf"

[vikingosegundo (manuel-vikingosegundo)]

I was able to make it work like this:

    u'fünf'.encode('latin-1')