Fixed theme install skip
Fixed theme install skip

http://wp-cli.org/commands/theme/is-installed/
error to theme install.
check result to is-installed command is return code, and stdout not be done write.
marushu/vccw,mimosafa/vccw,marushu/vccw,mimosafa/vccw,vccw-team/vccw,marushu/vccw,mimosafa/vccw,vccw-team/vccw,vccw-team/vccw