change port 5000 -> 8080 for HW4
step 0: add viewport and twitter bootstrap responsive css file
step 1: add navbar
remove old content, fix typos in previous commit
step 2: heading and subheading
index-final is the class version from
https://spark-public.s3.amazonaws.com/startup/code/bitstarter-hw4.html
remove blank line
step 3: video pitch
step 4: statistics
step 5: thermometer
step 6: social buttons