refactor HDFS state and it's tests. Add CheckpointState as the super trait of it
fix deleteOnExit
make sure to delete temp folder even when test fails
remove mix-in, use composition for CheckpointStore and CheckpointState
Merge branch 'release/0.5.1' into develop
Merge branch 'master' into develop
remove unnecessaru braces, reformat the comments to be less than 100 chars
reformat
fix tmp dir
Merge pull request #532 from tsdeng/refactor_hdfs_state

refactor HDFS state and it's tests
Removes some dead val's, confuses the logging
I ran into a strange deadlock in the parhashset, so just go with a simpler approach that has been more robust
New debug log messages when using a Summer constructor
Initial add of the generic optimizer code
Fix scala 2.9.3 compiler crash
Improve the Rule API, and add many tests

Added tests for HMap

Actually add the tests

Get the tests passing
Merge pull request #536 from twitter/removeDeadVals

Few small updates
Add several more example optimization rules
Add a HMap constructor, per Julien's suggestion
Fix a 2.10 compile issue