Bump to 0.1.20
Bump to 0.1.20

jbcrail/num,hauleth/num,rust-num/num-bigint,anchovieshat/num,achanda/num,anchovieshat/num,bluss/num,rust-num/num,vks/num,jbcrail/num,koverstreet/num,ollie27/rust_num,rust-num/num-bigint,koverstreet/num,rust-num/num-traits,Gustorn/num,rust-lang/num,DonSheddow/num,huonw/num,rust-num/num-integer,achanda/num,jdm/num,Ticki/num,DonSheddow/num,rust-num/num-traits,rust-lang/num,rust-num/num-integer,rust-num/num,Emerentius/num,vks/num