Modified the GuessDelimiter function.

Changed the GuessDelimiter function, so that a new delimiter is chosen as best if its delta value is higher than the current highest.
Added a testcase for decimal values with comma as decimal separator and pipes as delimiter.

But i couldnt ran the tests as i dont have a node interpreter installed, so i am not sure if the other tests dont break now.

papaparse.js

@@ -1262,7 +1262,7 @@ if (!Array.isArray)
 
 					if (typeof fieldCountPrevRow === 'undefined')
 					{
-						fieldCountPrevRow = fieldCount;
+						fieldCountPrevRow = 0;
 						continue;
 					}
 					else if (fieldCount > 1)
@@ -1275,7 +1275,7 @@ if (!Array.isArray)
 				if (preview.data.length > 0)
 					avgFieldCount /= (preview.data.length - emptyLinesCount);
 
-				if ((typeof bestDelta === 'undefined' || delta < bestDelta)
+				if ((typeof bestDelta === 'undefined' || delta > bestDelta)
 					&& avgFieldCount > 1.99)
 				{
 					bestDelta = delta;