Update cibuildwheel version = 0.8.0

Author: JorjMcKie

.travis.yml

@@ -36,7 +36,7 @@ matrix:
       prefix=/usr/local install && cd .."
     - export CIBW_ENVIRONMENT='CFLAGS=-fPIC'
 install:
-- "$PIP install cibuildwheel==0.7.2"
+- "$PIP install cibuildwheel==0.8.0"
 - mkdir mupdf && wget -q $MUPDF -O - | tar zx -C mupdf --strip-components=1
 - cp fitz/_mupdf_config.h mupdf/include/mupdf/fitz/config.h
 script: