hist: add set_sum_w2 and get_sum_w2 methods
hist: implement merge_bins method to merge arbitrary sets of bin windows
unit tests for merge_bins, overflow, and underflow
add bin merging example
Merge pull request #405 from ndawe/master

epic bin merging algorithm
Merge pull request #406 from ndawe/style

[MRG] style: missing SetPalette(1) in ATLAS and CMSTDR
examples: speedup for plot_bin_merging.py in batch mode
examples: tree_to_array.py speedup (use fewer entries)
examples: speedup chain_overwrite.py by using fewer files and entries in each
examples: speedup plot_autobinning.py in batch mode
Merge pull request #407 from ndawe/master

[MRG] speedup examples when in batch mode
fix issue #343: `from rootpy import ROOT` is not the same as `import rootpy.ROOT as ROOT`
ROOT.py: support both ROOT.TX for asrootpy'd ROOT lookup and and ROOT.X for direct rootpy lookup
ROOT.py: asrootpy automatically after __init__ to preserve ROOT's __init__
ROOT.py: add unit test
roosh: make all attributes of ROOT available in the LazyNamespace
ROOT.py: docs
mention ROOT.py in README.rst
Merge pull request #408 from ndawe/master

[MRG] rootpy.ROOT improvements
Merge pull request #409 from ndawe/roosh

[MRG] roosh: make all attributes of rootpy.ROOT available in the LazyNamespace