Regenerate gemspec for version 1.6.3
Regenerate gemspec for version 1.6.3

ixti/webmock,spjsschl/webmock,qrush/webmock,taiki45/webmock,arronmabrey/webmock,webmock/webmock,VincentZhao/webmock,henrik/webmock,hilben/webmock,avantcredit/webmock,bblimke/webmock,Omnihuron/webmock,sferik/webmock,sinisterstuf/webmock,maruware/webmock,xuwupeng2000/webmock,davidbegin/webmock,hobodave/webmock,influxdb/webmock