C file removal + cython build + Travis build cache

.gitignore

.travis.yml

Makefile

circle.yml

continuous_integration/install.sh

continuous_integration/test_script.sh

doc/developers/performance.rst

doc/whats_new.rst

setup.py

sklearn/__check_build/_check_build.c

sklearn/_build_utils/__init__.py

sklearn/_build_utils/cythonize.py

sklearn/_isotonic.c

sklearn/cluster/_dbscan_inner.cpp

sklearn/cluster/_hierarchical.cpp

sklearn/cluster/_k_means.c

sklearn/datasets/_svmlight_format.c

sklearn/decomposition/_online_lda.c

sklearn/decomposition/cdnmf_fast.c

sklearn/ensemble/_gradient_boosting.c