Fixes halgari#13 false values not unifying with lvar

+ add gitignore
+ fix a few tests that weren't comparing the output

.gitignore

@@ -0,0 +1,2 @@
+.lein-failures
+target/*

src/com/tbaldridge/odin/unification.clj

@@ -33,7 +33,7 @@
   (instance? LVar x))
 
 (defn walk [env a]
-  (if-let [a (get env a)]
+  (if-some [a (get env a)]
     (recur env a)
     a))
 

test/com/tbaldridge/odin_test.clj

@@ -26,11 +26,20 @@
       (is (= (set (o/for-query
                     (o/and (d/query data _ _ ?v)
                            (o/when (integer? ?v)))
-                    #{1 2 3}))))
+                    ?v))
+             #{1 2 3}))
 
       (is (= (set (o/for-query
                     (d/query data _ ?a _)
-                    #{:a :b :c :d :e :f :g})))))))
+                    ?a)) 
+             #{:a :b :c :d :e :f :g})))))
+
+(deftest false-in-data
+  (let [data [1 2 3 false]]
+    (is (= (set (o/for-query
+                  (d/query data _ _ ?val)
+                  ?val))
+            (set data)))))
 
 (o/defrule parent [data ?parent ?child]
   (o/and