DL-193: Bumped up the Guava version

Moving the Guava version from 16.0 to 20.0.

Author: arvindkandhare <arvind.kandhare@emc.com>

Reviewers: Henry Saputra <henry.saputra@gmail.com>, Sijie Guo <sijie@apache.org>

Closes #123 from arvindkandhare/guava_version
diff --git a/pom.xml b/pom.xml
index 7b6d58f..e3479bd 100644
--- a/pom.xml
+++ b/pom.xml
@@ -94,7 +94,7 @@
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
     <!-- dependencies -->
-    <bookkeeper.version>4.3.6-TWTTR-OSS</bookkeeper.version>
+    <bookkeeper.version>4.3.7-TWTTR-OSS</bookkeeper.version>
     <codahale.metrics.version>3.0.1</codahale.metrics.version>
     <commons-cli.version>1.1</commons-cli.version>
     <commons-codec.version>1.6</commons-codec.version>
@@ -102,7 +102,7 @@
     <commons-lang3.version>3.3.2</commons-lang3.version>
     <curator.version>3.2.1</curator.version>
     <finagle.version>6.34.0</finagle.version>
-    <guava.version>16.0</guava.version>
+    <guava.version>20.0</guava.version>
     <jetty.version>8.1.19.v20160209</jetty.version>
     <jmock.version>2.8.2</jmock.version>
     <junit.version>4.8.1</junit.version>