Added checkpoint parameter to JobTracker.

Now it's possible to set checkpoint=true for the Hadoop framework by
specifying mapred.mesos.checkpoint=true in the Hadoop config.

Review: https://reviews.apache.org/r/13091
Added role parameter to JobTracker.

Now it's possible to specify the framework role by setting
mapred.mesos.role.  The default role is "*".

Review: https://reviews.apache.org/r/13092
Updated Mesos mapred-site.xml for Hadoop.

Review: https://reviews.apache.org/r/13077
Simplified os::hostname() in libstout.

Review: https://reviews.apache.org/r/11108
Included pre/post-package hooks in Hadoop tutorial.

Review: https://reviews.apache.org/r/11110
Allowed ending Hadoop tutorial early.

You may also skip the test part by exporting SKIP_TESTS (i.e., 'make
hadoop SKIP_TESTS=1').

Review: https://reviews.apache.org/r/11111
Added check for Python.h in configure script.

Review: https://reviews.apache.org/r/11114
Switched to more portable paths for tutorial test.

Review: https://reviews.apache.org/r/11115
Shuffle offers before sending to frameworks.

This helps ensure fair allocation of resources.

Review: https://reviews.apache.org/r/11121
No longer accept offers on the same host/port.

We'll try to find a port combination that hasn't already been used to
launch a TaskTracker.

Review: https://reviews.apache.org/r/13080
Write Mesos JobTracker stats to state file.

Review: https://reviews.apache.org/r/11165/
s/hadoopJobs/jobs/g in Hadoop scheduler.

Review: https://reviews.apache.org/r/11489
Refactored Hadoop job completion.

Review: https://reviews.apache.org/r/11603
Stop tracker timer when we terminate tasks.

Review: https://reviews.apache.org/r/11604
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
Use XZ (LZMA) for package on Linuxes.

Review: https://reviews.apache.org/r/11112
Turned down noise from ZooKeeper.

Review: https://reviews.apache.org/r/11127
Fixed hadoop 0.20.205.0 dist.

Review: https://reviews.apache.org/r/11662
Allowed specification of mininum slot count.

To ensure Hadoop jobs begin promptly, we can specify a minimum number of
'hot slots' to be available for use.  This addresses the TaskTracker
spin up delay that exists with Hadoop on Mesos.  This can be a nuisance
with lower latency applications, such as ad-hoc Hive queries.

Review: https://reviews.apache.org/r/12921