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
Get flags for mesos-*.sh from build directory.
Added link to executor sandbox from framework template

The framework page is rendered with info from the master, but the
sandbox directory is known only by the slave. To link to the directory
from a page rendered by the master, create a page in between that acts
as a redirector by first asking for the directory from the slave.

If the sandbox is important for linking, the master could return
`executor.directory` in the `state.json` endpoint and negate the need
for this redirection stuff.

Review: http://reviews.apache.org/r/13006
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
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
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
Fixed broken build on GCC 4.8 due to -Wall.

With GCC 4.8, Boost fails to build from '-Wunused-local-typedefs', which
is implied by '-Wall'.

Review: https://reviews.apache.org/r/11974/