Refactored mesos-ps to display CPU and memory information.

From: Shingo Omura <everpeace@gmail.com>
Review: https://reviews.apache.org/r/15200
Refactored mesos-tail to use helpers from cli.py.

From: Shingo Omura <everpeace@gmail.com>
Review: https://reviews.apache.org/r/15336
Added a flash service for UI alerts after redirects.

When an error occurs during a redirect, it is useful to show an error
message on the following page view rather than the current one. In
particular, when clicking a sandbox link for a slave that is
inaccessible, the `SlaveExecutorRerouterCtrl` sends a request to the
desired slave and redirects back to root if an error occurs. It's not
possible to show an error during the redirect, and so rendering on
the root view is ideal.

Flash alerts are rendered once and then cleaned up; they will not
display more than once.

Review: http://reviews.apache.org/r/15198
Expanded stout::format() to handle 11 parameters.

From: Eric Biederman <ebiederm@xmission.com>
Review: https://reviews.apache.org/r/15013
Improved cgroups isolator to report additional memory statistics.

From: Eric Biederman <ebiederm@xmission.com>
Review: https://reviews.apache.org/r/15015
Fixed typos and errors in the Log Javadoc.
Added a note about the reliability of kill task requests.
Fixed typos in the Log javadoc.
Updated CHANGELOG for 0.15.0-rc4.
Updates powered by mesos list to include Devicescape, HubSpot, Vimeo, Pinkbike, and OpenTable.
Simplified os::hostname() in libstout.

Review: https://reviews.apache.org/r/11108
Shuffle offers before sending to frameworks.

This helps ensure fair allocation of resources.

Review: https://reviews.apache.org/r/11121
Added --enable-debug configure flag.

Review: https://reviews.apache.org/r/11605
Slave ping timeout may be increased by flags.

Review: https://reviews.apache.org/r/12885
Turned down noise from ZooKeeper.

Review: https://reviews.apache.org/r/11127
Use hostname instead of IP for redirection.

In the Web UI, the redirection does not work for hosts where the local
interface address is not publicly accessible.  For example, with EC2 the
redirection will not work.

This change writes the Master's hostname into ZooKeeper, thereby
allowing the redirection to work with private IP addresses.

Review: https://reviews.apache.org/r/11975/
On recovery fail, do rm -rf /tmp/mesos/meta.
Use libstout cache for slave completedFrameworks.

The list of retired (completed) frameworks is now a stout cache rather
than a boost circular buffer.  There are now key iterator accessors for
the cache class, and a removal member.

Review: https://reviews.apache.org/r/13599
Added a slave load hint for scheduler sorting.

With this change, the offers will include a slave load hint based on the
5 minute load average for that slave (returned from getloadavg()).
Frameworks can use this hint to select among otherwise similar offers,
as an optimization.

Review: https://reviews.apache.org/r/13675
Increase web UI reload delay.