"Running setup.py...egg_info" log: INFO => DEBUG

Change log level of `"Running setup.py (path:%s) egg_info"` log messages
from INFO to DEBUG. The average user does not know or care that pip is
running `python setup.py egg_info`, unless things are broken, IMHO.

See: GH-1070
Merge pull request #2177 from msabramo/egg_info_log_debug_instead_of_info

"Running setup.py...egg_info" log: INFO => DEBUG