Adding the functionality to print the access logs to a log file.

Sign-off: @mumia

By adding the access-log project, we are able to get the access logs with one single line in robinInit.js.
 accesslog(req, res); 

No changes to robin.js is made.

Logs are appended to the file (default: robin.log) mentioned in Robin. Nothing printed to console.

This file includes the access logs in NCSA Common log format.
https://en.wikipedia.org/wiki/Common_Log_Format
127.0.0.1 - - [10/Jan/2014:10:56:19 -0000] "GET /Lisbon/Large-historical-newly-refurbished-student-residence-in-Estrela_10348_listing.html HTTP/1.1" 200 - "http://localhost:8000/Lisbon/7-brand-new-rooms-exclusively-for-students-in-Santos_10568_listing.html" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:26.0) Gecko/20100101 Firefox/26.0"