Merge pull request #65 from sthadka/master

Handle HttpError when using get_headers in elli_http
Add elli:set_callback to reconfigure middlewares
Merge pull request #67 from chrisavl/master

Make elli callback reconfigurable
typed callbacks for dialyzer
Added types to some records.
Added a Makefile for elli development.
Eunit in makefile
Merge pull request #68 from anha0825/makefile

Makefile and some types for records
Handle/explain request_timeout in elli_example_callback.
Correct path to include file.
Makes this file compilable from the erlang shell.
Use proc_lib:spawn instead of spawn for more info in crash report.
Info about the creator of this processes, sibling processes
and more info regarding the crash will be displayed.
Note: This does not affect crases in the user code, these are catched by elli.
For more info on proc_lib, look here:
http://www.erlang.org/doc/man/proc_lib.html
Merge pull request #69 from anha0825/proc_lib

spawn processes with proc_lib