Do not return error if removing bind mount fails.

Review: https://reviews.apache.org/r/28339
Set memory::limit_in_bytes first, even with limitSwap enabled.

Review: https://reviews.apache.org/r/28305
Changed RunTaskWithCommandInfoWithUser to not use shell.

The 'nobody' user is restricted on some systems from shell access and
broke the task.user tests (which have been disabled since then).  With
the command.shell field, the test can run the command directly.

Review: https://reviews.apache.org/r/26894
Allow mesos containerizer to destroy correctly at each state.

Review: https://reviews.apache.org/r/28141
Fix style issue for mesos containerizer commit.
Allowed slave to checkpoint resources.

Review: https://reviews.apache.org/r/26990
Fixed a compilation error on gcc-4.4.

Review: https://reviews.apache.org/r/28357
Fix deadlock between SocketManager::send() and internal::send().

This was a deadlock between the 'this' and 'processes' synchronized
blocks that occured because the .then() on socket futures can be
invoked immediately with the new implementation of io::poll().

Review: https://reviews.apache.org/r/28367
Add thread local to short-circuit run_in_event_loop().

This improves performance by short-circuiting run_in_event_loop() to
just call the lambda if it is already in the event loop.

Review: https://reviews.apache.org/r/28184
Added a reviewboard config to make ./support/post-reviews easier to use.

Review: https://reviews.apache.org/r/28298
Extracted and genralized WhitelistWatcher.

WhitelistWatcher can be used for tracking changes to all kind of
whitelists. In order to reuse the functionality, extract the code from
master sources.

Review: https://reviews.apache.org/r/28230
Fixed typos in comments for example module implementation.

Review: https://reviews.apache.org/r/28420
Updated WhitelistWatcher to watch only if a file is given.

Whitelist may be represented either by a filepath or a by a wildcard.
In the latter case WhitelistWatcher should not constantly try reload
the whitelist.

Review: https://reviews.apache.org/r/28442
Removed some DiskInfo validations from C++ Resources in favor of doing
them in the master.

Review: https://reviews.apache.org/r/28429