There was a problem passing colors to cairo_set_source_rgb.
Should be floats between 0 and 1.
Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

Thanks to Roland Schatz for the patch.

Rename major/minor/rev to plugin_major/plugin_minor/plugin_rev to
avoid a conflict with the major/minor macros in sys/types.h

Thanks to J. Commelin for the patch.

Thanks to J. Commelin for the patch.

1) zoom-center :: bool
   zoom-center = false

   If zoom-center = false nothing changes.
   If zoom-center = true zooming respects the horizontal center of the
   pageview. That is, the vertical line dividing the displayed part of
   the document doesn't move within the document.

   Reasoning: When viewing a pdf with a margin we usually want to hide the
   margin at both sides by zooming in.

2) scroll-hstep :: float
   scroll-hstep = -1

   If scroll-hstep < 0 nothing changes.
   If scroll-hstep >= 0 then scroll-hstep defines the scroll step in the
   horizontal direction.

   Reasoning: This allows us to make finer adjustments in the horizontal
   direction without the mouse and without loosing the ablility to
   navigate quickly through the document.

3) search-hadjust :: bool
   search-hadjust = true

   If search-hadjust = true nothing changes.
   If search-hadjust = false searching does not adjust the horizontal
   center of the document when showing search results.

   Reasoning: When viewing a pdf with a margin we usually want to hide
   the margin at both sides by zooming in. The horizontal adjustment
   sometimes hides parts of the document by moving the horizontal
   center.

Closes #228.

Thanks to Martin Pelikan.

Fixes #220