Update link to "XBase File Format Description"

Updated link to "XBase File Format Description"  to address Issue #12: Documentation URL not valid #12.  Link now properly links.

Author: jzmiller1

README.md

@@ -13,8 +13,7 @@ dfs/shapefile.pdf](http://www.esri.com/library/whitepapers/pdfs/shapefile.pdf)
 . The Esri document describes the shp and shx file formats. However a third
 file format called dbf is also required. This format is documented on the web
 as the "XBase File Format Description" and is a simple file-based database
-format created in the 1960's. For more on this specification see: [http://www.
-clicketyclick.dk/databases/xbase/format/index.html](http://www.clicketyclick.d
+format created in the 1960's. For more on this specification see: [http://www.clicketyclick.dk/databases/xbase/format/index.html](http://www.clicketyclick.d
 k/databases/xbase/format/index.html)
 
 Both the Esri and XBase file-formats are very simple in design and memory