Check for configured index directory

Before attempting to write an index first check to see if the
directory configuration exists. This corrects the current behavior
of attempting to write to a path such as '/exhibitor-XXX' which
unless exhibitor is being run as root will not be able to write to.
Merge pull request #126 from joewilliams/index_path_check

Check for configured index directory
Merge pull request #128 from Randgalt/master

1.4.8 release
[Gradle Release Plugin] - pre tag commit:  '1.4.8'.
[Gradle Release Plugin] - new version commit:  '1.4.9-SNAPSHOT'.
Updated build scripts to correct version