Fix typo (thanks @rdmurphy)
diff --git a/plugins/available/virtualenv.plugin.bash b/plugins/available/virtualenv.plugin.bash
index 2636963..1625915 100644
--- a/plugins/available/virtualenv.plugin.bash
+++ b/plugins/available/virtualenv.plugin.bash
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-# make sure virtualenvwrapper is enabled if availalbe
+# make sure virtualenvwrapper is enabled if available
 [[ `which virtualenvwrapper.sh` ]] && . virtualenvwrapper.sh
 
 # create a new virtualenv for this directory