Change to core 1.5.7 snapshot

Change-Id: I35e2db38ba01613c445cbbc587d27c63cdda367c
Reviewed-on: http://review.couchbase.org/91926
Reviewed-by: Subhashni Balakrishnan <[email protected]>
Tested-by: Subhashni Balakrishnan <[email protected]>

Author: bsubhashni

pom.xml

@@ -28,7 +28,7 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
 
-        <core.version>1.5.6</core.version>
+        <core.version>1.5.7-SNAPSHOT</core.version>
         <junit.version>4.12</junit.version>
         <mockito.version>1.10.19</mockito.version>
         <slf4j.version>1.7.7</slf4j.version>