Auto merge of #127 - fitzgen:publish-on-crates-io, r=asajeffrey

Version bump for crates.io

r? @asajeffrey

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/mozjs/127)
<!-- Reviewable:end -->

Author: bors-servo

Cargo.toml

@@ -2,7 +2,7 @@
 name = "mozjs_sys"
 description = "System crate for the Mozilla SpiderMonkey JavaScript engine."
 repository = "https://github.com/servo/mozjs/"
-version = "0.0.0"
+version = "0.50.0"
 authors = ["Mozilla"]
 links = "mozjs"
 build = "build.rs"