Fix switch to ipython console when importing rootpy.interactive

Delay the instantiation of InteractiveShellEmbed until
first usage.
Merge pull request #260 from apuignav/rootpy-issue-259

Fix switch to ipython console when importing rootpy.interactive
Fix NameError in root-hadd when file exists.
Merge pull request #263 from scottstvnsn/root-hadd-nameerr

Fix NameError in root-hadd when file exists
don't break super update in TreeBuffer(OrderedDict)
add ignore_branches kwarg to TreeChain
Merge pull request #261 from ndawe/master

MRG: A few minor changes
fix infinite recursion in File.__getattr__ reported in #264
Merge pull request #266 from ndawe/master

Fix #264
use super() throughout
more concise __init__
Merge pull request #267 from ndawe/super

super() rootpy
fix ravel, matplotlib with log scale y axis, cut to pytables where syntax
Merge pull request #268 from ndawe/master

fix Hist.ravel(), matplotlib with log scale y axis, Cut.where syntax
flush the hdf5 file in addition to the tables
Merge pull request #271 from ndawe/hdf5

root2hdf5: a few minor improvements
incremental fixes for #269
fix the cloning of Plottables
fork fewer processes in file lock test
fix TreeTests: TFile.Close the temp files but keep the tempfile descriptors open