Fix validate url path

Change validate url path to /api/push/validate/
Update README.md

Added note about modification to fix validate API path.
Update pom.xml

Set version to 0.1.3.XOOM and add Xoom information.
Fix validate URL path in unit test and fix package in another unit test.
Merged changes from rlubbat

Merge branch 'master' of github.com:xoom/urbanairship-java-library into SUPPORT-1747-validate-url

Conflicts:
	pom.xml
Fixed API validation URL error

- Fixed exception with APIResponse, since return payload has changed
- updated tests
Merge pull request #8 from urbanairship/SUPPORT-1747-validate-url

SUPPORT-1747 Validation URL
Updated CHANGELOG for v0.2.1
[maven-release-plugin] prepare release v0.2.1
[maven-release-plugin] prepare for next development iteration