Incorrectly setting HADOOP_HOME can cause unclear errors

[bwhite]

The HADOOP_HOME should end in a slash, if set like the following hadoop streaming can't be found. This should

1. Be louder that hadoop streaming can't be found
2. Be more tolerant of not having a slash when trying to find hadoop streaming

brandyn@vitrieve03:/projects/hadoopy$ export HADOOP_HOME=/usr/lib/hadoop
brandyn@vitrieve03:/projects/hadoopy$ python
Python 2.7.1+ (r271:86832, Apr 11 2011, 18:13:53)
[GCC 4.5.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.

import hadoopy
a=hadoopy.readtb('/user/brandyn/playground/kernels/15').next()
Traceback (most recent call last):
File "", line 1, in
StopIteration