Allow completions for vars in '.' namespace

Modify the regex for recognizing potential var names to allow for
namespaces starting with the '.' character. It is quite a popular choice
to put utility functions in the '.' namespace so that they are globally
available; for examples see [1] and [2]. Even though this may not be
officially supported, it is a good idea to support completions for this
namespace.

[1]: https://github.com/zcaudate/vinyasa
[2]: https://github.com/palletops/lein-shorthand

src/compliment/sources/ns_mappings.clj

@@ -8,7 +8,7 @@
 (defn var-symbol?
   "Test if prefix resembles a var name."
   [x]
-  (re-matches #"([^\.\/\:][^\.\/]*([^\/\:]*\/[^\.\/]*)?)?" x))
+  (re-matches #"([^\/\:][^\.\/]*([^\/\:]*\/[^\.\/]*)?)?" x))
 
 (defn dash-matches?
   "Tests if prefix partially matches a var name with dashes as