Update README.md

Added a space in the pregenerated URL so that the link does not break in most readers.

README.md

@@ -18,7 +18,7 @@ The full repository sources are available at https://github.com/OGCMetOceanDWG/W
 Pre-Generated PNGs
 ------------------
 
-A set of pre-generated PNGs are available for download at http://www.slashgeo.org/sites/all/files/WorldWeatherSymbols-png.zip.
+A set of pre-generated PNGs are available for download at http://www.slashgeo.org/sites/all/files/WorldWeatherSymbols-png.zip .
 
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