Add tests for markup parsing.
Update example in README.
Add 'nosubset' property for fonts.
POSSIBLY INCOMPATIBLE: Fix issue #10. The difference will only
be noticable when you query the width for centered/right
aligned texts.
UNLIKELY INCOMPATIBLE: method set_pango_scale does now enable/disable.
The scaling is fixed to PANGO_SCALE (1024).
Fixed some issues with pango scaling.
Fix regression that sometimes tripled the resultant PDF.