Use WriteConcern/SAFE by default

WriteConcern/NORMAL is ridiculously dangerous and most apps simply do not have performance
requirements to justify completely ignoring server responses.

src/monger/core.clj

@@ -26,7 +26,7 @@
 
 (declare ^:dynamic ^Mongo        *mongodb-connection*)
 (declare ^:dynamic ^DB           *mongodb-database*)
-(def     ^:dynamic ^WriteConcern *mongodb-write-concern* WriteConcern/NORMAL)
+(def     ^:dynamic ^WriteConcern *mongodb-write-concern* WriteConcern/SAFE)
 
 
 ;;
@@ -84,6 +84,11 @@
   (def ^:dynamic *mongodb-database* db))
 
 
+(defn set-write-concern!
+  [wc]
+  (def ^:dynamic *mongodb-write-concern* wc))
+
+
 
 (defprotocol Countable
   (count [this] "Returns size of the object"))

test/monger/test/collection.clj

@@ -44,6 +44,7 @@
 
 (use-fixtures :each purge-people-collection purge-docs-collection purge-things-collection purge-libraries-collection)
 
+(monger.core/set-write-concern! WriteConcern/SAFE)
 
 ;;
 ;; insert

test/monger/test/stress.clj

@@ -27,6 +27,8 @@
 ;; Tests
 ;;
 
+(monger.core/set-write-concern! WriteConcern/NORMAL)
+
 (deftest insert-large-batches-of-documents-without-object-ids
   (doseq [n [1000 10000 100000]]
     (let [collection "things"