Initialize offset to zero in FT2Font::make_open_args

Clang warns that it gets a garbage value on Python 2, since
mpl_PyFile_Dup expands to a function call that does not use &offset.
It seems that the value is not used on Python 2 but it doesn't
cost much to silence the warning.
Silence some writable-string warnings

Cast string constants explicitly to (char*) since the
method calls aren't going to modify the strings.
Check the return values of mpl_PyFile_DupClose
Remove dead assignment

The value initially assigned to pix was never used.
Remove dead assignments in _image.cpp
Disable copying of C++ classes with nontrivial destructors

http://stackoverflow.com/questions/4172722/what-is-the-rule-of-three
Merge pull request #2991 from jkseppan/tidyup-ft2font

Silence some compiler warnings related to ft2font
Merge pull request #2992 from jkseppan/tidyup-misc

Remove a few dead assignments
Merge pull request #2997 from jkseppan/rule-of-three

Disable copying of C++ classes with nontrivial destructors
Added functionality for plotting the actual violin bodies to violinplot.
Added ksdensity (KDE) function in mlab and adapted _axes violinplot function to accept new KDE.
Added basic violinplot demo in examples
Added lines to the violinplot function
Fixed mean/median for kde dict result
Added flags to violinplot which toggle whether various values of interest are displayed on the violin plots
Fixed pep8 compliance in ksdensity
Added horizontal violin plot feature compatible with means, extremas and medians.
Fixed bug for regression test #1181 in scipy unit tests; ksdensity is now referred to as gaussian_kde and exists as a class in mlab.
Fixed list comp position bug and updated examples
Reverted 69b304c.
Re-added points parameter to violinplot.
Fixed several style issues.
Merging for pep8 compliance for mlab's GaussianKDE