calculate % changed

[bartveneman]

• How many of the metrics have changed? (in %)
• How much % has each of the metrics changed?

[bartveneman]

diff src/index.js test/index.js | diffstat
 unknown |  180 ++++++++++++++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 148 insertions(+), 32 deletions(-)