Depend on newer version of Guava. Guava 17 is more than 2 years old

[tswast]

Guava 17 was released on 2014-04-22 according to
https://github.com/google/guava/wiki/ReleaseHistory

I had to start excluding it as a dependency to use the latest version of Guava. GoogleCloudPlatform/java-docs-samples@6569349

If the reason the client is using v17 is that it is the latest release that supports JDK5, note that JDK5 has been end-of-life since October 20009. http://www.oracle.com/technetwork/java/eol-135779.html

[mattwhisenhunt]

#1070 addressed this issue.