Replaces unescaped symbols in <code>str</code>. For example, the '$' symbol
will be replaced in 'item$count', but not in 'item\$count'.
@param {String} str Original string
@param {String} symbol Symbol to replace
@param {String} replace Symbol replacement. Might be a function that
returns new value
@return {String}
function(str, symbol, replace) {
			var i = 0;
			var il = str.length;
			var sl = symbol.length;
			var matchCount = 0;
				
			while (i < il) {
				if (str.charAt(i) == '\\') {
					// escaped symbol, skip next character
					i += sl + 1;
				} else if (str.substr(i, sl) == symbol) {
					// have match
					var curSl = sl;
					matchCount++;
					var newValue = replace;
					if (_.isFunction(replace)) {
						var replaceData = replace(str, symbol, i, matchCount);
						if (replaceData) {
							curSl = replaceData[0].length;
							newValue = replaceData[1];
						} else {
							newValue = false;
						}
					}
					
					if (newValue === false) { // skip replacement
						i++;
						continue;
					}
					
					str = str.substring(0, i) + newValue + str.substring(i + curSl);
					// adjust indexes
					il = str.length;
					i += newValue.length;
				} else {
					i++;
				}
			}
			
			return str;
		}