PyPI (pip installation) setup for 0.6 code (#1445)

* force gcc-5 or clang-omp for Mac OS, prepare for pip pack

* add sklearn dep, make -j4

* finalize PyPI submission

* revert to Xcode clang for passing build #1468

* force to clang, try to solve cmake travis error

* remove sklearn dependency

python-package/setup_pip.py

@@ -34,8 +34,8 @@ LIB_PATH = libpath['find_lib_path']()
 # and be sure to test it firstly using "python setup.py register sdist upload -r pypitest"
 setup(name='xgboost',
       # version=open(os.path.join(CURRENT_DIR, 'xgboost/VERSION')).read().strip(),
-      version='0.4a30',
-      description=open(os.path.join(CURRENT_DIR, 'README.rst')).read(),
+      version='0.6a2',
+      description='XGBoost Python Package',
       install_requires=[
           'numpy',
           'scipy',