Add cwdbase option to enable file base to match cwd.

By setting cwdbase: true, all files returned from glob will have a relative path being relative to the cwd. This is useful if you want perform operations on multiple directories relative to the cwd and not relative to the lowest glob expression.

Example:
gulp.src(["lib/**", "bin/**"], { cwd: process.cwd, cwdbase: true }).pipe(gulp.dest("/mydest/"));

This will result in /mydest/lib/<lib files> and /mydest/bin/<bin files> compared to /mydest/<lib and bin files>