Fail when no command provided with shell enabled in docker.

Review: https://reviews.apache.org/r/24987
Fixed MasterZooKeeperTest.LostZooKeeperCluster.

Review: https://reviews.apache.org/r/25195
Fixed a bug in the allocator which could cause filters to be
unnecessarily installed.

Review: https://reviews.apache.org/r/25207
Added instructions for getting started with CentOS.

Review: https://reviews.apache.org/r/25272
Added Resources support to return the port range for the given number of ports.

Review: https://reviews.apache.org/r/24810
Updated the container failed to launch error message in the slave.

Review: https://reviews.apache.org/r/25273
Count pending tasks as staging in the slave.

Review: https://reviews.apache.org/r/25302
Fixed a bug in the staging tasks metric.

Review: https://reviews.apache.org/r/25303
Removed an unnecessarily introduced Option.

Review: https://reviews.apache.org/r/25304
Flattened the executor resoures when launching executors.

Review: https://reviews.apache.org/r/25306
Fixed the memory limitation construction.
Improved the error message when destroying a container.

Review: https://reviews.apache.org/r/25344
Minor update to include package config file

Minor update to include package config file

Review: https://reviews.apache.org/r/25355
Added optional --offer_timeout to rescind unused offers.

The ability to set an offer timeout helps prevent unfair resource
allocations in the face of frameworks that hoard offers, or that
accidentally drop offers.

When optimistic offers are added, hoarding will not affect the
fairness for other frameworks.

Review: https://reviews.apache.org/r/22066
Fix protobuf detection on systems with Python 3 as default

MESOS-1774

Review: https://reviews.apache.org/r/25439
Added kill() to freezerTimedOut() in cgroups.cpp.
This is a short-term fix for MESOS-1758.

Review: https://reviews.apache.org/r/25457
common/attributes: Add a helper function for seeing if this set of attributes is a superset of that set of attributes
Allow reconfiguring slaves (Changing attribuets and resources) ad-hoc

Added a method tryReconfigure to Slave which updates the local config
and propogates it out to the master. The master takes the updated
config and persists it in the Registrar.

This changed the assumption in mesos that slaveInfo is an immutable
struct.

The risk is mitigated by only allowing strict supersets of attributes
and resources to be set. You can do things like increase the number of
CPUs a machine has, but not decrease them.

There is one case we cannot guard against with that, and that is if a
framework is doing a negative check for a attribute of a node
(Checking that an attribute doesn't exist), the framework will
possibly get a node which didn't use to have that attribute but now
does.

The implementation starts by updating the attributes locally, then
propogates them outward (the main master, the replicated master log),
so the new properties effectively end up being eventually consistent.
Remove c++11 auto
Address reviewer comments