fix crash when a file doesn't exit in static folder.

my bad, previous patch was buggy
made ip address to bind to configurable
Add charset specification support to boss_mail.
Change error logging to use lager
Merge
Merge pull request #392 from zkessin/master

Merging some contributer pull requests
merge
Merge pull request #391 from fdevibe/charset-email-support

Add charset specification support to boss_mail.
cowboy server doen't start properly
fix cowboy static

thix fix depend on previous fix https://github.com/ChicagoBoss/ChicagoBoss/pull/393
add template error logging

ChicagoBoss/ChicagoBoss#379
Merge #394
Merge #393
fixed case
merge
Merge pull request #395 from zkessin/master

merging in pull requests
document new_from_json/2

fix #373
Merge pull request #396 from zkessin/master

document new_from_json/2
provide a detailed error if there is a template issue

fix ChicagoBoss/ChicagoBoss#379
Merge pull request #397 from zkessin/master

provide a detailed error if there is a template issue