[ImgBot] Optimize images

*Total -- 824.59kb -> 720.21kb (12.66%)

/graphs/web7/response-time-day.png -- 12.29kb -> 4.19kb (65.87%)
/graphs/web1/response-time-day.png -- 11.62kb -> 4.14kb (64.4%)
/graphs/web5/response-time-day.png -- 11.74kb -> 4.42kb (62.38%)
/graphs/web6/response-time-day.png -- 11.31kb -> 4.27kb (62.23%)
/graphs/thundersquared/response-time-day.png -- 10.03kb -> 4.39kb (56.21%)
/graphs/web2/response-time-day.png -- 9.29kb -> 4.43kb (52.24%)
/graphs/web4/response-time-day.png -- 9.26kb -> 4.48kb (51.58%)
/graphs/web2/response-time-week.png -- 14.31kb -> 12.19kb (14.83%)
/graphs/thundersquared/response-time-week.png -- 13.67kb -> 11.64kb (14.83%)
/graphs/web1/response-time-week.png -- 13.47kb -> 11.60kb (13.84%)
/graphs/web4/response-time-week.png -- 13.66kb -> 11.77kb (13.83%)
/graphs/web7/response-time-week.png -- 12.79kb -> 11.11kb (13.16%)
/graphs/web5/response-time-week.png -- 14.00kb -> 12.17kb (13.1%)
/graphs/web6/response-time-week.png -- 12.76kb -> 11.28kb (11.65%)
/graphs/web1/response-time-month.png -- 23.93kb -> 21.26kb (11.16%)
/graphs/web6/response-time-year.png -- 35.27kb -> 31.42kb (10.91%)
/graphs/web6/response-time.png -- 35.27kb -> 31.42kb (10.91%)
/graphs/web2/response-time.png -- 34.45kb -> 30.76kb (10.71%)
/graphs/web2/response-time-year.png -- 34.45kb -> 30.76kb (10.71%)
/graphs/web6/response-time-month.png -- 24.08kb -> 21.78kb (9.57%)
/graphs/web7/response-time-month.png -- 25.81kb -> 23.47kb (9.06%)
/graphs/web2/response-time-month.png -- 26.15kb -> 23.89kb (8.63%)
/graphs/web4/response-time-month.png -- 25.59kb -> 23.60kb (7.78%)
/graphs/thundersquared/response-time-month.png -- 26.36kb -> 24.38kb (7.52%)
/graphs/web5/response-time-month.png -- 26.33kb -> 24.50kb (6.94%)
/graphs/web7/response-time-year.png -- 38.45kb -> 35.84kb (6.77%)
/graphs/web7/response-time.png -- 38.45kb -> 35.84kb (6.77%)
/graphs/web5/response-time-year.png -- 38.33kb -> 35.90kb (6.32%)
/graphs/web5/response-time.png -- 38.33kb -> 35.90kb (6.32%)
/graphs/thundersquared/response-time.png -- 38.46kb -> 36.08kb (6.17%)
/graphs/thundersquared/response-time-year.png -- 38.46kb -> 36.08kb (6.17%)
/graphs/web4/response-time.png -- 22.89kb -> 22.42kb (2.06%)
/graphs/web4/response-time-year.png -- 22.89kb -> 22.42kb (2.06%)
/graphs/web1/response-time-year.png -- 30.24kb -> 30.20kb (0.12%)
/graphs/web1/response-time.png -- 30.24kb -> 30.20kb (0.12%)

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