improve replace performance take 2 (this time I have confirmed substantial improvements in the profiler)

lib/buffer-search.js

@@ -95,17 +95,27 @@ class BufferSearch {
         replacePattern = escapeHelper.unescapeEscapeSequence(replacePattern);
       }
 
+      const replacementChunks = [];
+      const text = this.editor.getText();
+      const buffer = this.editor.getBuffer();
+
+      let end = 0;
+
       for (let i = 0, n = markers.length; i < n; i++) {
-        const marker = markers[i]
+        const marker = markers[i];
         const bufferRange = marker.getBufferRange();
-        const replacementText = findRegex ?
-          this.editor.getTextInBufferRange(bufferRange).replace(findRegex, replacePattern) :
-          replacePattern;
-        this.editor.setTextInBufferRange(bufferRange, replacementText);
+        const start = buffer.characterIndexForPosition(bufferRange.start);
+        replacementChunks.push(text.substring(end, start));
+        end = buffer.characterIndexForPosition(bufferRange.end);
+        replacementChunks.push(findRegex ?
+          text.substring(start, end).replace(findRegex, replacePattern)
+          : replacePattern);
 
         marker.destroy();
         this.markers.splice(this.markers.indexOf(marker), 1);
       }
+      replacementChunks.push(text.substring(end));
+      this.editor.setText(replacementChunks.join(''));
     });
 
     return this.emitter.emit('did-update', this.markers.slice());