Fix validation failed for cookbook name. Remove unsupported pip -E option 

Hi,

I made two changes. 

1. Fix validation failed for cookbook name
This is a simliar change to https://github.com/halkeye/application_ruby/commit/d0a8254b3ae6f8dd9e226ca2dcbfbf003baafda7

2. Remove unsupported pip -E option
pip 1.2.1 doesn't support "-E" option. And the code already taking care of "pip install" into the virtualenv folder; so no need to use "-E" anymore. 

Thanks,
Kinkoi Lo