INTEXT-107 Upgrade to Spring Integration 4.0

JIRA: https://jira.spring.io/browse/INTEXT-107

* Upgrade to Gradle 1.12
* Fix compile warnings
* Fix XSD declaration
* Get rid of `EasyMock`
INTEXT-73 Sending multipart SMS messages through a SMPP provider using sar_msg_ref_num, sar_segment_seqnum and sar_total_segments
minor optimization
added test for multipart messages

Signed-off-by: Edge Dalmacio <edgar.dalmacio@gmail.com>