Added 'mesos-scp' CLI command.

The CLI command mesos-scp uses scp to copy the specified local file(s)
to a specified directory on all slaves known by the current master.

From: Du Li <lidu008@gmail.com>
Review: https://reviews.apache.org/r/14963
Fixed an exception raised in the master related to task statuses.

Review: https://reviews.apache.org/r/16038
Fixed group to use 32 bit signed integers for sequence numbers.

Review: https://reviews.apache.org/r/16045
Fixed the flaky FaultToleranceTest.SlaveReregisterOnZKExpiration test.
Fixed MESOS-870: The slave's http endpoint can crash the slave.

Review: https://reviews.apache.org/r/16072
Fixed the master to drop authentication when non-leading.

Review: https://reviews.apache.org/r/16068
Fixed the flaky FaultTolerance.SlaveReliableRegistration test.
Minor fix for script-without-shebang: MESOS-831.

From: Timothy St. Clair <tstclair@redhat.com>
Review: https://reviews.apache.org/r/15764
Added loadavg() convenience method to stout.

This patch includes a wrapper to get system load averages in uptime(1)
format. This is used by an upcoming patch which expose these averages
over master and slave stats.json endpoints.

Review: https://reviews.apache.org/r/15653
Fixed the python tests in the presence of muliple eggs.

Review: https://reviews.apache.org/r/16136
Added stringifier.hpp to stout/Makefile.am.

Review request #15285 breaks 'make distcheck' due to missing entry in
3rdparty/libprocess/3rdparty/stout/Makefile.am for the new stringifier
header. This patch adds the missing entry.

Review: https://reviews.apache.org/r/16161
Printed timezone, full ISO 8601, with timestamps.

The current date format, "2013-12-05 10:08:30", does not include the
timezone and can be confusing when the timezone is different than
expected. Add the timezone and the letter "T" between the date and time
to match the ISO 8601 standard.

"2013-12-05 10:08:30" -> "2013-12-05T10:08:30-0800"

Review: http://reviews.apache.org/r/16096
Added min/max functions to stout which take two Options.

From: Jie Yu <yujie.jay@gmail.com>
Review: https://reviews.apache.org/r/16158
Fixed shell scripts to assume bash.

Review: https://reviews.apache.org/r/16164
Fixed some copy / paste mistakes in the ExecutorDriver javadoc.
Added more overloaded functions of min/max in Option.

From: Jie Yu <yujie.jay@gmail.com>
Review: https://reviews.apache.org/r/16225
Added a WeakFuture<T>.

Using a WeakFuture<T> fixes memory leaks in Future::then and
Promise::associate.

From: Jie Yu <yujie.jay@gmail.com>
Review: https://reviews.apache.org/r/16197
Made all relative dates relative to poll time.

When Angular tries to resolve a filter, it runs it twice to see if the
value changes. Without passing a reference date to `relativeDate`, the
function instantiates a new `Date` to use as the reference. In the
surprisingly frequent case when rendering occurs on the edge of a minute,
dozens of `relativeDate` calls will return two different values if the
filter is resolved before- and after the minute edge.

For example:

    Render starts at 12:13:59.999
    $digest calls relativeDate, returns "1 minute ago"
    $digest calls relativeDate 1ms later, returns "2 minutes ago"
    Angular throws, "Error: 10 $digest() iterations reached. Aborting!"

By passing the pollTime to all relative dates, the dates are all
relative to the same moment in time, and $digest always resolves
properly.

Note: Because page rendering is unfortunately painfully slow on some
pages when there is lots of data, this case happens frequently.

Review: http://reviews.apache.org/r/16185
Fixed a bug in the task status accounting.

Review: https://reviews.apache.org/r/16188
Fixed the flaky AllocatorTest.RoleTest.