Check for failed allocations in libhdfs code

This commit adds checks for failed allocations in hdfs.c for Hadoop
versions 1.x.  Version 2.x seem to be ok.
Merge pull request #44 from ilveroluca/libhdfs_check_allocations

Check for failed allocations in libhdfs code
New test to showing effect of not releasing the Python GIL
Enable new test in suite
Release GIL around many hdfs calls
Remove excessive printing from unit test
More tests for the hdfs GIL change
Merge pull request #45 from ilveroluca/threading

Release GIL around hdfs calls with network access
Lower data size used in test_hdfs.thread_allow to run on TravisCI
Fix run_wordcount_* scripts

This commit makes them work with both the 'hdfs' and 'hadoop fs'
commands, and it removes the unix-like options that were being passed to
'hdfs' (the 'hadoop dfs' command doesn't understand them)
If HADOOP_BIN is defined, add it to the PATH in TravisCI set-up
Since they're identical, remove duplicate config directories for 2.2 and 2.4
For Travis, set mapred.task.timeout to one minute
If HADOOP_BIN defined by installation, then add it to the PATH
Added HADOOP_BIN & HADOOP_SBIN to PATH
Lower the acceptable count threshold in thread test to 5

The tests were sometimes failing on TravisCI (slower machines) with
counts below 100.  A test where we left the GIL locked showed that the
counter value doesn't change at all across calls, so in theory even an
increment of 1 would demonstrate that the mechanism is working.
Set the PYTHONPATH on hadoop-env.sh
Explicit PYTHONPATH in the travis environment
Fixed PATH on hadoop_env.sh
Reactived virtualenv after the python-all-dev installation