Performed GTEST_IS_THREADSAFE check.

Review: https://reviews.apache.org/r/11264
Removed unnecessary use of Option.

Review: https://reviews.apache.org/r/11265
Refactored zookeeper_tests.cpp into master_detector_tests.cpp and
group_tests.cpp.

Review: https://reviews.apache.org/r/11266
Made tests flags inherit from logging.

Review: https://reviews.apache.org/r/11267
Moved 'tests::mkdtemp' to Environment.

Review: https://reviews.apache.org/r/11268
Minor cleanup in stout/exit.hpp.

Review: https://reviews.apache.org/r/11269
Improved library for using JVM/JNI and updated uses (in tests).

Review: https://reviews.apache.org/r/11270
Removed unused variables in AllocatorZooKeeperTest.

Review: https://reviews.apache.org/r/11271
Renamed tests/zookeeper_test.hpp|cpp to zookeeper.hpp|cpp.

Review: https://reviews.apache.org/r/11272
Refactored MesosTest/MesosClusterTest into a generic fixture for
launching in-memory Mesos clusters and updated all tests
appropriately.

Review: https://reviews.apache.org/r/11273
Cleaned up the output from running and automagically disabling the
CgroupsNoHierarchyTest.

Review: https://reviews.apache.org/r/11274
Used Milliseconds rather than Duration::parse.

Review: https://reviews.apache.org/r/11275
Removed unnecessary TestingIsolators.

Review: https://reviews.apache.org/r/11276
A little spring cleaning in the allocator tests.

Review: https://reviews.apache.org/r/11278
More spring cleaning, this time in the slave recovery tets.

Review: https://reviews.apache.org/r/11279
Replaced local::launch in tests with MesosTest.

Review: https://reviews.apache.org/r/11280
Removed unused local::launch overload.

Review: https://reviews.apache.org/r/11281
Cleanups in configure.ac.

Review: https://reviews.apache.org/r/11282
Refactored base 'State' implementation to be serialization agnostic
and use a 'Storage' instance. Changed the LevelDB and ZooKeeper
implementations to implement 'Storage' instead of 'State'. Provided a
protobuf specific implementation on top of 'State'. Updated code
(including JNI) and tests accordingly.

Review: https://reviews.apache.org/r/11308
Added a 'port' field to SlaveInfo and updated default master and slave
ports.

Review: https://reviews.apache.org/r/11309