Press the + or SPACE to add a line of text. Press the = to print the final command. Press the □ to edit the command type, a piece of text or color. Press the - to remove a certain pair. You can press "l" to see a full list of all the available colors that will work. Select the command and press "CTRL" and "C" to copy the command and "CTRL" and "V" to paste it into Minecraft.
REMEMBER! You may need to add a bold tag if you want bold text ("color":"green","bold":true}). Also, you need to add a space after each line of text in order to add a space in the full command (text 1:Hi_ , text 2:There or it will come out as HiThere). Obviously, you can edit it however you like! Thanks to @RoboPig for the challenge! Feel free to post your creation in the comments! 26/10/2015: Added title & subtitle 26/10/2015: Added remove button 26/10/2015: Fixed remove button glitch and other minor bugs.