Merge pull request #612 from ndawe/master

misc improvements
Merge pull request #613 from ndawe/master

plot_corrcoef_matrix improvements
Merge pull request #614 from ndawe/master

add bootstrapping example
Only split draw expression on single colons

The expression passed to `TTree.Draw()` is split on colons to change the
axis ordering from ROOT's `y:x` to the more conventional `x:y`.  However
this mangles expressions containing the C++ scope operator `::`, such as
`var_A:TMath::Exp(var_B)`.  This commit modifies this behaviour to
ignore multiple adjacent colons, and split only on single colons.
Merge pull request #615 from stevensons/colons-in-draw-expr

Only split draw expression on single colons
hist: transfer GetEntries in uniform_binned()
Merge pull request #617 from ndawe/dev

hist: transfer GetEntries in uniform_binned()
legend positioning
better legend positioning
improved legend positioning
updates
add test for split_norm_shape
histfactory sys_names simplification
add missing GetZaxis to HistStack and add divisions property to Axis
plot_bootstrap.py: slower framerate and fix zaxis