MISC address Gael's comments
DOC added comment about default for n_nonzero_coefs.
documentation for partial dependence plots
add module imports
typo
TEST: decrease precision in test_lars_drop_for_good

If the test is wrong, this will be well off. Small errors just reflect
numerical errors
cosmit
call pl.show
renamed datasets.cal_housing to datasets.california_housing
FIX: lars drop for good platform specific test failure
FIX + ENH: catch custom function argument errors and inform user

- added expception in case a user passes a non-tuple returning function and does not supply the derrivatives via fun_prime
- added an example on the custom function type expected to the docs
- added regression tests and positive tests
FIX #1354: machine precision assertion failure in test_liblinear_random_state
Merge branch 'master' of github.com:scikit-learn/scikit-learn
add plot titles
cosmit
Merge branch 'master' into gbrt-interactions
cosmit: docstrings
better narrative docs for partial dependence
cosmit: footnote header
empty instead of zeros