Add build test for serde feature
Add build test for serde feature

rust-num/num-integer,rust-num/num-integer,rust-num/num-bigint,rust-num/num-traits,rust-num/num-traits,rust-lang/num,DonSheddow/num,rust-num/num-bigint,koverstreet/num,rust-num/num,DonSheddow/num,vks/num,vks/num,rust-lang/num,koverstreet/num,rust-num/num