Improve code performance

[ramyaragupathy]

Performance now:

File	Ramya's parser	JSON.parse	Gap
twitter.json	4.869ms	0.249ms	19 times
facebook.json	26.584ms	1.815ms	14 times
openstreetmap.json	145.779ms	17.619ms	8 times
package.json	1.485ms	0.155ms	9 times
rap.json	24.396ms	0.646ms	37 times
caliper.json	23.766ms	0.776ms	30 times

String and number values perform better because there's no string slicing. Need to modify array parser & object parser to iterate over index