Specify exact versions in Cargo.toml

To fix "cargo check" on travis, where they have silently upgraded us
from Ring 0.13.2 to 0.13.4, which has some errors.

Cargo.toml

@@ -9,28 +9,28 @@ name = "deno"
 version = "0.1.12"
 
 [dependencies]
-atty = "0.2.11"
-dirs = "1.0.4"
+atty = "=0.2.11"
+dirs = "=1.0.4"
 flatbuffers = { path = "third_party/flatbuffers/rust/flatbuffers/" }
-futures = "0.1.25"
-getopts = "0.2.18"
-http = "0.1.13"
-hyper = "0.12.13"
+futures = "=0.1.25"
+getopts = "=0.2.18"
+http = "=0.1.13"
+hyper = "=0.12.13"
 # The current version of hyper-rustls, 0.14.0, depends on tokio-core, which is
 # deprecated.
 hyper-rustls = { git = "https://github.com/ctz/hyper-rustls.git" }
-lazy_static = "1.1.0"
-libc = "0.2.43"
-log = "0.4.6"
-rand = "0.5.5"
-remove_dir_all = "0.5.1"
-rustyline = "2.1.0"
-ring = "0.13.2"
-tempfile = "3.0.4"
-tokio = "0.1.11"
-tokio-executor = "0.1.5"
-tokio-fs = "0.1.4"
-tokio-io = "0.1.10"
-tokio-process = "0.2.3"
-tokio-threadpool = "0.1.8"
-url = "1.7.1"
+lazy_static = "=1.1.0"
+libc = "=0.2.43"
+log = "=0.4.6"
+rand = "=0.5.5"
+remove_dir_all = "=0.5.1"
+rustyline = "=2.1.0"
+ring = "=0.13.2"
+tempfile = "=3.0.4"
+tokio = "=0.1.11"
+tokio-executor = "=0.1.5"
+tokio-fs = "=0.1.4"
+tokio-io = "=0.1.10"
+tokio-process = "=0.2.3"
+tokio-threadpool = "=0.1.8"
+url = "=1.7.1"