Delete unused commonSuffixLength binary search code

See https://github.com/sergi/go-diff/issues/54#issuecomment-343002957

Closes #54

diffmatchpatch/diff.go

diff --git a/diffmatchpatch/diff.go b/diffmatchpatch/diff.go
index 82ad7bc..897ab67 100644
--- a/diffmatchpatch/diff.go
+++ b/diffmatchpatch/diff.go
@@ -434,6 +434,7 @@
 
 // commonPrefixLength returns the length of the common prefix of two rune slices.
 func commonPrefixLength(text1, text2 []rune) int {
+	// Linear search. See comment in commonSuffixLength.
 	short, long := text1, text2
 	if len(short) > len(long) {
 		short, long = long, short
@@ -448,6 +449,8 @@
 
 // commonSuffixLength returns the length of the common suffix of two rune slices.
 func commonSuffixLength(text1, text2 []rune) int {
+	// Use linear search rather than the binary search discussed at https://neil.fraser.name/news/2007/10/09/.
+	// See discussion at https://github.com/sergi/go-diff/issues/54.
 	n := min(len(text1), len(text2))
 	for i := 0; i < n; i++ {
 		if text1[len(text1)-i-1] != text2[len(text2)-i-1] {
@@ -455,27 +458,6 @@
 		}
 	}
 	return n
-
-	// TODO research and benchmark this, why is it not activated? https://github.com/sergi/go-diff/issues/54
-	// Binary search.
-	// Performance analysis: http://neil.fraser.name/news/2007/10/09/
-	/*
-	   pointermin := 0
-	   pointermax := math.Min(len(text1), len(text2))
-	   pointermid := pointermax
-	   pointerend := 0
-	   for pointermin < pointermid {
-	       if text1[len(text1)-pointermid:len(text1)-pointerend] ==
-	           text2[len(text2)-pointermid:len(text2)-pointerend] {
-	           pointermin = pointermid
-	           pointerend = pointermin
-	       } else {
-	           pointermax = pointermid
-	       }
-	       pointermid = math.Floor((pointermax-pointermin)/2 + pointermin)
-	   }
-	   return pointermid
-	*/
 }
 
 // DiffCommonOverlap determines if the suffix of one string is the prefix of another.