Issue #14: Introduce asynchronous http client for the login system.
Issue #14: Added new variables to startup_config along with connection pool option.
Issue #14: Added requirements to travis.yml
Fix the build issue for travis.
Refactoring header map, login path, curl handle.
Fixing accidental removal of curl initialization.
Removed mutex as well as curl global init as it is already present in fserv.cpp.
Refactoring curl_escape_string and curl instance handle into the login class.
Issue #14: Merge branch ConcurrentLogin