Fix HTML plot reporter image in README
Use imgur link for plot
Add -keepalive flag to toggle persistent conns

The flag is enabled by default.

closes #89
Fix fmt of bool for go vet
Add a comment to make go lint happy
Improve keepalive flag usage comment
Merge pull request #90 from jpfuentes2/jf_fix_plot_img

Fix HTML plot reporter image in README
Merge pull request #91 from jpfuentes2/jf_keepalive_option

Add -keepalive flag to toggle persistent conns
lib/attack: Remove redundant re-assignment
Update README
Don't treat 3xx status codes as errors

Fixes #88
Account for Target reading in Latency measurements
Use exact tick time for Timestamp
Update go vet dep url
Only test latest stable Go release