Add READMEs to Cargo.toml files

This will cause crates.io to render each crate's README as its
information page.

bellman/Cargo.toml

@@ -1,6 +1,7 @@
 [package]
 authors = ["Sean Bowe <ewillbefull@gmail.com>"]
 description = "zk-SNARK library"
+readme = "README.md"
 documentation = "https://github.com/ebfull/bellman"
 homepage = "https://github.com/ebfull/bellman"
 license = "MIT/Apache-2.0"

ff/Cargo.toml

@@ -3,6 +3,7 @@ name = "ff"
 version = "0.4.0"
 authors = ["Sean Bowe <ewillbefull@gmail.com>"]
 description = "Library for building and interfacing with finite fields"
+readme = "README.md"
 documentation = "https://docs.rs/ff/"
 homepage = "https://github.com/ebfull/ff"
 license = "MIT/Apache-2.0"

group/Cargo.toml

@@ -5,6 +5,7 @@ authors = [
     "Sean Bowe <ewillbefull@gmail.com>",
     "Jack Grigg <jack@z.cash>",
 ]
+readme = "README.md"
 license = "MIT/Apache-2.0"
 
 description = "Elliptic curve group traits and utilities"

librustzcash/Cargo.toml

@@ -7,6 +7,7 @@ authors = [
     "Jay Graber <jay@z.cash>",
     "Simon Liu <simon@z.cash>"
 ]
+readme = "README.md"
 edition = "2018"
 
 [lib]

pairing/Cargo.toml

@@ -7,6 +7,7 @@ authors = [
     "Sean Bowe <ewillbefull@gmail.com>",
     "Jack Grigg <jack@z.cash>",
 ]
+readme = "README.md"
 license = "MIT/Apache-2.0"
 
 description = "Pairing-friendly elliptic curve library"

zcash_client_backend/Cargo.toml

@@ -4,6 +4,7 @@ version = "0.0.0"
 authors = [
     "Jack Grigg <jack@z.cash>",
 ]
+readme = "README.md"
 edition = "2018"
 
 [dependencies]

zcash_primitives/Cargo.toml

@@ -4,6 +4,7 @@ version = "0.0.0"
 authors = [
     "Jack Grigg <jack@z.cash>",
 ]
+readme = "README.md"
 edition = "2018"
 
 [dependencies]

zcash_proofs/Cargo.toml

@@ -4,6 +4,7 @@ version = "0.0.0"
 authors = [
     "Jack Grigg <jack@z.cash>",
 ]
+readme = "README.md"
 edition = "2018"
 
 [dependencies]