split, Array and write target word

Instead of writing the target word as a text string, it's broken up
into its constituent letters and then written into the target box as
spans.
track inputs

Code now creates a new array of both target word and answer word. A for
loop goes through and compares the contents of each array against one
another by the index of the array. If it matches, attach CSS color
green. If not then make it the default black.
Merge pull request #39 from yuanphoon/16_input_tracking

16 input tracking