Optimize pythoninstaller

force create syslink to overwrite old installation
use portable function definition

Signed-off-by: Harrison Feng <feng.harrison@gmail.com>
bump version to 0.1.2

Signed-off-by: Harrison Feng <feng.harrison@gmail.com>
add pip_installer

Pip is not default installed to py2.x, manually installation is needed.
We create a script to setup pip and virtualenv in py2.x

Signed-off-by: Harrison Feng <feng.harrison@gmail.com>
correct yum install command options

Signed-off-by: Harrison Feng <feng.harrison@gmail.com>
use verbose options args in pip install

Signed-off-by: Harrison Feng <feng.harrison@gmail.com>
make sure pip bin can be found

Signed-off-by: Harrison Feng <feng.harrison@gmail.com>
merge 0.1.2 changes to master