Added the library typesafe config to read default config values. The order followed is system properties, asynchttpclient.properties and then defaultahc.properties. defaultahc.properties has all the default values for each of the configuration properties and these could either be overridden by a system property or asynchttpclient.properties
Merge pull request #645 from salilsurendran/master

Added the typesafe config to read default config values