changed context of column.formatter() to column

Prior to this change, there is no way to identify column.field
from the formatter. The context (this) of column.formatter()
was table.header. which served no practical purpose.

src/bootstrap-table.js

@@ -952,11 +952,13 @@
             this.data = s ? $.grep(this.data, function (item, i) {
                 for (var key in item) {
                     key = $.isNumeric(key) ? parseInt(key, 10) : key;
-                    var value = item[key];
+                    var value = item[key],
+                        column = that.options.columns[getFieldIndex(that.options.columns, key)],
+                        j = $.inArray(key, that.header.fields);
 
                     // Fix #142: search use formated data
-                    value = calculateObjectValue(that.header,
-                        that.header.formatters[$.inArray(key, that.header.fields)],
+                    value = calculateObjectValue(column,
+                        that.header.formatters[j],
                         [value, item, i], value);
 
                     var index = $.inArray(key, that.header.fields);
@@ -1290,7 +1292,7 @@
 
                 style = sprintf('style="%s"', csses.concat(that.header.styles[j]).join('; '));
 
-                value = calculateObjectValue(that.header,
+                value = calculateObjectValue(column,
                     that.header.formatters[j], [value, item, i], value);
 
                 // handle td's id and class