rely on failure 0.1.2 from git to get backtrace disabled by default

without relying on an unreleased 1.0 API.  Trying to get rid of the special
chucklefish hack branches in the meantime before 1.0.

CHANGELOG.md

@@ -23,8 +23,6 @@
   breaking *user* invariants.
 - Several Lua stack checking bugs have been fixed that could have lead to
   unsafety in release mode.
-- `rlua` now depends on `failure` 1.0 and `cc` 1.0, and does not enable the
-  failure `backtrace` feature by default.
 
 ## [0.13.0]
 - Small API incompatible change which fixes unsafety: Scope and scope created

Cargo.toml

@@ -26,7 +26,7 @@ builtin-lua = ["cc"]
 
 [dependencies]
 libc = { version = "0.2" }
-failure = { git = "https://github.com/rust-lang-nursery/failure", version = "1.0" }
+failure = { git = "https://github.com/rust-lang-nursery/failure", version = "0.1.2" }
 compiletest_rs = { version = "0.3", optional = true }
 
 [build-dependencies]