update instructions for unit-test.arc v1.0

Author: akkartik

index.md

@@ -47,6 +47,7 @@ title: Arc Programming Language
 <span style='color:grey'>$</span> git clone <a href='http://github.com/arclanguage/anarki'>http://github.com/arclanguage/anarki</a>
 <span style='color:grey'>$</span> cd anarki
 <span style='color:grey'>$</span> hg clone <a href='https://bitbucket.org/zck/unit-test.arc'>https://bitbucket.org/zck/unit-test.arc</a>
+<span style='color:grey'>$</span> cd unit-test.arc; hg update v1.0; cd ..
 <span style='color:grey'>$</span> ./arc.sh
 <span style='color:grey'>arc&gt;</span> (help do)  <span style='color:blue'>; online help</span>
 [mac] (do . args)