SPARK-1806: Upgrade Mesos dependency to 0.18.1

Enabled Mesos (0.18.1) dependency with shaded protobuf

Why is this needed?
Avoids any protobuf version collision between Mesos and any other
dependency in Spark e.g. Hadoop HDFS 2.2+ or 1.0.4.

Ticket: https://issues.apache.org/jira/browse/SPARK-1806

* Should close https://issues.apache.org/jira/browse/SPARK-1433

Author berngp

Author: Bernardo Gomez Palacio <bernardo.gomezpalacio@gmail.com>

Closes #741 from berngp/feature/SPARK-1806 and squashes the following commits:

5d70646 [Bernardo Gomez Palacio] SPARK-1806: Upgrade Mesos dependency to 0.18.1