Merge pull request #28 from srmerritt/master

Don't crash in leptus:running_listeners/0 if there are no listeners
Add tests for three internal functions of leptus_handler module
Fix type spec of leptus_logger:add_handler/2

Add leptus_logger:delete_handler/2
Fix type spec of leptus_logger:delete_handler/2
Document leptus_logger module
Update start.org data types
Add a note to 'Configuration' documentation
Keep used options in an ETS table
Add leptus:upgrade/3 to use options when upgrading a listener
Fix placing dependencies in the right directory

Fix moving deps/*/deps/* to the deps directory
Thanks, @jfacorro
Allow passing in cowboy_protocol:opts()

 - Create 'start_listener/4' that accepts ProtoOpts for cowboy
 - Include default 'env' that is currently being set
Merge pull request #32 from ptuckey/cowboy-proto-opts

Allow passing in cowboy_protocol:opts()
Add mailing-list information to README.org
Fix mailing-list link
Merge pull request #1 from s1n4/master

Merge upstream changes from s1n4
Use cowboy 1.0.1
merge