Updated Travis-CI conf to avoid 'brew upgrade' error. Using pre-installed xctool instead.
Updated Travis-CI conf to avoid 'brew upgrade' error. Using pre-installed xctool instead.

ThomWee/OHHTTPStubs,tarbrain/OHHTTPStubs,bruceflowers/OHHTTPStubs,manuyavuz/OHHTTPStubs,hirohisa/OHHTTPStubs,tarbrain/OHHTTPStubs,kazmasaurus/OHHTTPStubs,sessuru/OHHTTPStubs,sessuru/OHHTTPStubs,liufeigit/OHHTTPStubs,HyprMXMobile/OHHTTPStubs,JinlianWang/OHHTTPStubs,oenius/OHHTTPStubs,SummerHanada/OHHTTPStubs,liufeigit/OHHTTPStubs,hirohisa/OHHTTPStubs,virajs/OHHTTPStubs,SummerHanada/OHHTTPStubs,bruceflowers/OHHTTPStubs,ThomWee/OHHTTPStubs,hirohisa/OHHTTPStubs,tarbrain/OHHTTPStubs,virajs/OHHTTPStubs,kazmasaurus/OHHTTPStubs,manuyavuz/OHHTTPStubs,tarbrain/OHHTTPStubs,oenius/OHHTTPStubs,HyprMXMobile/OHHTTPStubs,ThomWee/OHHTTPStubs,manuyavuz/OHHTTPStubs,hirohisa/OHHTTPStubs,HyprMXMobile/OHHTTPStubs,virajs/OHHTTPStubs,SummerHanada/OHHTTPStubs,JinlianWang/OHHTTPStubs,virajs/OHHTTPStubs,liufeigit/OHHTTPStubs,sessuru/OHHTTPStubs,oenius/OHHTTPStubs,vladzz/OHHTTPStubs,JinlianWang/OHHTTPStubs,ThomWee/OHHTTPStubs,bruceflowers/OHHTTPStubs,HyprMXMobile/OHHTTPStubs,JinlianWang/OHHTTPStubs,oenius/OHHTTPStubs,kazmasaurus/OHHTTPStubs,SummerHanada/OHHTTPStubs