bump lazycell and env_logger to latest versions (#619)

diff --git a/Cargo.toml b/Cargo.toml
index 4a37e21..2c1be1a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -23,7 +23,7 @@
 default = ["with-deprecated"]
 
 [dependencies]
-lazycell = "0.4.0"
+lazycell = "0.5.0"
 log      = "0.3.1"
 slab     = "0.3.0"
 net2     = "0.2.29"
@@ -42,7 +42,7 @@
 kernel32-sys = "0.2"
 
 [dev-dependencies]
-env_logger = { version = "0.3.0", default-features = false }
+env_logger = { version = "0.4.0", default-features = false }
 tempdir    = "0.3.4"
 bytes      = "0.3.0"