Regex formatters don't track position

[jcubic]

Issue summary

Simple regex formatters don't handle position, so it work like it in fact change the position (you can't move the cursor inside replaced text).

Expected behavior

You should move the cursor on text created using regex formatter

Actual behavior

you can click on first character of the replaced text

Steps to reproduce

1. Execute:

 $.terminal.new_formatter([
     /foo/g, '[[;green;]foo]'
 ]);
 $.terminal.new_formatter(function(str, options) {
     return [str.replace(/bar/g, '[[;green;]bar]'), options.position];
 });
 term.insert('foo bar');

2. you can only click o letter "f" in foo but on any character in bar

[jcubic]

The problem is more complex it don't work if there are two formatters and one change the length of the string.