travis: Use GTest 1.7.0
travis: Use GTest 1.7.0

Fixes compilation in Yosemite

kevinhendricks/gumbo-parser,google/gumbo-parser,aleksandaratanasov/gumbo-parser,mcanthony/gumbo-parser,urandu/gumbo-parser,Sigil-Ebook/sigil-gumbo,kevinhendricks/gumbo-parser,lvchao0428/gumbo-parser,f123h456/gumbo-parser,luoxn28/gumbo-parser,lvchao0428/gumbo-parser,Sigil-Ebook/sigil-gumbo,abc00/gumbo-parser,luoxn28/gumbo-parser,mcanthony/gumbo-parser,Sigil-Ebook/sigil-gumbo,aleksandaratanasov/gumbo-parser,kevinhendricks/gumbo-parser,luoxn28/gumbo-parser,kevinhendricks/gumbo-parser,f123h456/gumbo-parser,abc00/gumbo-parser,aleksandaratanasov/gumbo-parser,lvchao0428/gumbo-parser,mcanthony/gumbo-parser,f123h456/gumbo-parser,mcanthony/gumbo-parser,urandu/gumbo-parser,aleksandaratanasov/gumbo-parser,abc00/gumbo-parser,kevinhendricks/gumbo-parser,google/gumbo-parser,luoxn28/gumbo-parser,luoxn28/gumbo-parser,aleksandaratanasov/gumbo-parser,f123h456/gumbo-parser,lvchao0428/gumbo-parser,google/gumbo-parser,abc00/gumbo-parser,urandu/gumbo-parser,lvchao0428/gumbo-parser,urandu/gumbo-parser,google/gumbo-parser,abc00/gumbo-parser,mcanthony/gumbo-parser,Sigil-Ebook/sigil-gumbo,f123h456/gumbo-parser,google/gumbo-parser,urandu/gumbo-parser,Sigil-Ebook/sigil-gumbo