Use the 'at' method instead of 'flat' method

[maeema]

The implementation of #119.

[hazzik]

Please run grunt to generate output.txt file. That file contains the lengths of resulting characters. Then play with alignment (adding 0, NaN, 'true', 'false', 'undefined' at the start of the expression to reduce number of characters required to get index). For example: (<something>)[9] => (0+<something>)[10]