[package] stax-api is added twice

Library stax-api is added twice in final ZIP file.
It's due to the dependency tree.

```
[INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ elasticsearch-cloud-azure ---
[INFO] org.elasticsearch:elasticsearch-cloud-azure:jar:2.5.2-SNAPSHOT
[INFO] +- org.hamcrest:hamcrest-core:jar:1.3.RC2:test
[INFO] +- org.hamcrest:hamcrest-library:jar:1.3.RC2:test
[INFO] +- com.carrotsearch.randomizedtesting:randomizedtesting-runner:jar:2.1.10:test
[INFO] |  \- junit:junit:jar:4.10:test
[INFO] +- org.apache.lucene:lucene-test-framework:jar:4.10.2:test
[INFO] |  +- org.apache.lucene:lucene-codecs:jar:4.10.2:test
[INFO] |  +- org.apache.lucene:lucene-core:jar:4.10.2:compile
[INFO] |  +- com.carrotsearch.randomizedtesting:junit4-ant:jar:2.1.6:test
[INFO] |  \- org.apache.ant:ant:jar:1.8.2:test
[INFO] +- org.elasticsearch:elasticsearch:jar:1.4.2:compile
[INFO] |  +- org.apache.lucene:lucene-analyzers-common:jar:4.10.2:compile
[INFO] |  +- org.apache.lucene:lucene-queries:jar:4.10.2:compile
[INFO] |  +- org.apache.lucene:lucene-memory:jar:4.10.2:compile
[INFO] |  +- org.apache.lucene:lucene-highlighter:jar:4.10.2:compile
[INFO] |  +- org.apache.lucene:lucene-queryparser:jar:4.10.2:compile
[INFO] |  +- org.apache.lucene:lucene-sandbox:jar:4.10.2:compile
[INFO] |  +- org.apache.lucene:lucene-suggest:jar:4.10.2:compile
[INFO] |  +- org.apache.lucene:lucene-misc:jar:4.10.2:compile
[INFO] |  +- org.apache.lucene:lucene-join:jar:4.10.2:compile
[INFO] |  +- org.apache.lucene:lucene-grouping:jar:4.10.2:compile
[INFO] |  \- org.apache.lucene:lucene-spatial:jar:4.10.2:compile
[INFO] |     \- com.spatial4j:spatial4j:jar:0.4.1:compile
[INFO] +- com.microsoft.windowsazure:microsoft-windowsazure-api:jar:0.4.6:compile
[INFO] |  +- com.sun.jersey:jersey-client:jar:1.13:compile
[INFO] |  |  \- com.sun.jersey:jersey-core:jar:1.13:compile
[INFO] |  +- javax.inject:javax.inject:jar:1:compile
[INFO] |  +- com.sun.jersey:jersey-json:jar:1.13:compile
[INFO] |  |  +- org.codehaus.jettison:jettison:jar:1.1:compile
[INFO] |  |  |  \- stax:stax-api:jar:1.0.1:compile
[INFO] |  |  +- com.sun.xml.bind:jaxb-impl:jar:2.2.3-1:compile
[INFO] |  |  |  \- javax.xml.bind:jaxb-api:jar:2.2.2:compile
[INFO] |  |  |     \- javax.xml.stream:stax-api:jar:1.0-2:compile
[INFO] |  |  +- org.codehaus.jackson:jackson-core-asl:jar:1.9.2:compile
[INFO] |  |  +- org.codehaus.jackson:jackson-mapper-asl:jar:1.9.2:compile
[INFO] |  |  +- org.codehaus.jackson:jackson-jaxrs:jar:1.9.2:compile
[INFO] |  |  \- org.codehaus.jackson:jackson-xc:jar:1.9.2:compile
[INFO] |  +- commons-logging:commons-logging:jar:1.1.1:compile
[INFO] |  +- javax.mail:mail:jar:1.4.5:compile
[INFO] |  |  \- javax.activation:activation:jar:1.1:compile
[INFO] |  \- org.apache.commons:commons-lang3:jar:3.1:compile
[INFO] +- log4j:log4j:jar:1.2.17:compile
[INFO] \- org.elasticsearch:elasticsearch:test-jar:tests:1.4.2:test
```

We should exclude `javax.xml.stream:stax-api:jar:1.0-2:compile` from `com.microsoft.windowsazure:microsoft-windowsazure-api:jar:0.4.6:compile`

Closes #56.

(cherry picked from commit 68efe93)
(cherry picked from commit 68f25d1)

Author: dadoonet

pom.xml

@@ -71,6 +71,12 @@ governing permissions and limitations under the License. -->
             <groupId>com.microsoft.windowsazure</groupId>
             <artifactId>microsoft-windowsazure-api</artifactId>
             <version>0.4.6</version>
+            <exclusions>
+                <exclusion>
+                    <groupId>javax.xml.stream</groupId>
+                    <artifactId>stax-api</artifactId>
+                </exclusion>
+            </exclusions>
         </dependency>
 
         <dependency>