Initialize project setting for Volleyer
Add Assert Util class
[Issue-123] Add http model classes
[Issue-124] Add VolleyerContext class
[Issue-125] Add builder classes which are available for method-chaining style
Add IoUtils
[Issue-127] Add NetworkResponseParser interface
[Issue-128] Add implementations of NetworkResponseParser
Add getHeaders() into HttpContent
[Issue-129] Add VolleyerRequest
[Issue-130] Add RequestCreator interface
[Issue-131] Add DefaultRequestCreator class
[Issue-132] Add getRequestCreator() method into VolleyerContext
Add Volleyer class
[Issue-133] Modify ResponseBuilder.execute() to use RequestCreator
[Issue-134] Add RequestExecutor interface
[Issue-135] Add DefaultRequestExecutor class
[Issue-136] Add getRequestExecutor() in VolleyerContext
[Issue-141] Modify ResponseBuilder.execute() to use RequestExecutor
[Issue-142] Modify ResponseBuilder.execute() to check whether listener, errorListener or responseParser and set a default instance if null