Improve object reader/writer. Add compression.

Cargo.lock

@@ -107,6 +107,15 @@ version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8aebca1129a03dc6dc2b127edd729435bbc4a37e1d5f4d7513165089ceb02634"
 
+[[package]]
+name = "crc32fast"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ba125de2af0df55319f41944744ad91c71113bf74a4646efff39afe1f6842db1"
+dependencies = [
+ "cfg-if",
+]
+
 [[package]]
 name = "digest"
 version = "0.9.0"
@@ -126,6 +135,18 @@ dependencies = [
  "version_check",
 ]
 
+[[package]]
+name = "flate2"
+version = "1.0.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "766d0e77a2c1502169d4a93ff3b8c15a71fd946cd0126309752104e5f3c46d94"
+dependencies = [
+ "cfg-if",
+ "crc32fast",
+ "libc",
+ "miniz_oxide",
+]
+
 [[package]]
 name = "generic-array"
 version = "0.14.4"
@@ -179,6 +200,7 @@ version = "0.1.0"
 dependencies = [
  "digest",
  "error-chain",
+ "flate2",
  "serde",
  "sha2",
  "tempfile",