Document how insignificant parameters work

 * Document how two Tasks with the same params are identical
 * Document how significant=False changes the signature
Merge pull request #262 from onlynone/master

Document how insignificant parameters work
hive hackery; pushes hive query output to stdout in hadoop.py, which in turn gets written to the output of the hive task. Note that the hive task now requires an output to be specified, even if there is no output (ie a create table command is used or somesuch