Example of svg id being supplied, better input handling of svg ids

samples/load_images.rb

@@ -10,5 +10,10 @@ Squib::Deck.new(width: 825, height: 1125, cards: 1) do
   # SVGs can be scaled too
   svg file: 'spanner.svg', x: 50, y: 50, width: 250, height: 250
 
+  # We can also limit our rendering to a single object, if the SVG ID is set
+  # Squib prepends a #-sign if one is not specified
+  svg file: 'spanner.svg', id: '#backdrop', x: 50, y: 350, width: 75, height: 75
+  svg file: 'spanner.svg', id: 'backdrop', x: 50, y: 450, width: 125, height: 125
+
   save prefix: 'load_images_', format: :png
 end

samples/spanner.svg

@@ -10,7 +10,7 @@
    viewBox="0 0 128 128"
    id="svg2"
    version="1.1"
-   inkscape:version="0.48.4 r9939"
+   inkscape:version="0.48.3.1 r9886"
    width="100%"
    height="100%"
    sodipodi:docname="spanner.svg">
@@ -36,15 +36,15 @@
      guidetolerance="10"
      inkscape:pageopacity="0"
      inkscape:pageshadow="2"
-     inkscape:window-width="1680"
-     inkscape:window-height="988"
+     inkscape:window-width="1280"
+     inkscape:window-height="1002"
      id="namedview14"
      showgrid="false"
      inkscape:zoom="2.8284271"
      inkscape:cx="98.928938"
      inkscape:cy="62.194589"
-     inkscape:window-x="1432"
-     inkscape:window-y="109"
+     inkscape:window-x="1912"
+     inkscape:window-y="-8"
      inkscape:window-maximized="1"
      inkscape:current-layer="g3767"
      inkscape:document-units="in"
@@ -60,8 +60,9 @@
        x="5.3126979"
        height="501.3746"
        width="501.3746"
-       id="rect3765"
-       style="fill:#000000;fill-opacity:1;fill-rule:nonzero;stroke:#000000;stroke-width:10.62539577;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-opacity:1;stroke-dasharray:none;stroke-dashoffset:0" />
+       id="backdrop"
+       style="fill:#000000;fill-opacity:1;fill-rule:nonzero;stroke:#000000;stroke-width:10.62539577;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-opacity:1;stroke-dasharray:none;stroke-dashoffset:0"
+       inkscape:label="#rect3765" />
     <path
        style="fill:#000000;fill-opacity:1;fill-rule:nonzero;stroke:none"
        d="M 36.267098,-7.709219 C 16.393265,5.1318032 3.2161811,27.462365 3.2161811,52.884128 c 0,39.825874 32.2852369,72.111092 72.1110909,72.111092 23.870397,0 44.964938,-11.67699 58.089488,-29.545518 -11.26063,7.275808 -24.65607,11.517748 -39.060173,11.517748 -39.825853,0 -72.11109,-32.285221 -72.11109,-72.111095 0,-15.95546 5.248882,-30.6218942 14.021601,-42.565574 z"