add support for mail module

See http://wiki.nginx.org/Modules#Mail_modules

Sample Usage:

 nginx::resource::mailhost { 'domain1.example':
   ensure      => present,
   auth_http   => 'server2.example/cgi-bin/auth',
   protocol    => 'smtp',
   listen_port => 587,
   ssl_port    => 465,
   starttls    => 'only',
   xclient     => 'off',
   ssl         => 'true',
   ssl_cert    => '/tmp/server.crt',
   ssl_key     => '/tmp/server.pem',
 }
Merge pull request #41 from oxilion/jfryman-add-mail-support

add support for mail module
Fixed typo in init.pp
Merge pull request #42 from igoraj/master

Fixed typo in init.pp
ssl check fixed
removing wrong boolean quoting
removing wrong boolean quoting
indentation
Merge pull request #43 from zoide/ssl-fixes

Ssl fixes
more boolean comparison fixes
Merge pull request #44 from zoide/ssl-fixes

more boolean comparison fixes
Create Chapter 1 - The haunting Beginning
Rename Chapter 1 - The haunting Beginning to Chapter 1 - The haunting Beginning.md
Update Chapter 1 - The haunting Beginning.md
Add support for upstream_cfg_prepend

Makes things possible like specifying ip_hash and/or keepalive.
Merge pull request #47 from oxilion/upstream_cfg_prepend

Add support for upstream_cfg_prepend
Changed SSL ciphers to the recent default for Nginx which is much
    more secure
Added SSL caching to speed up SSL requests
Add server_tokens to the global config so this can be turned on|off
    between dev and prod
Add proxy_set_header to vhost as different vhosts may require different
    headers and the global setting is not ideal
Minor space formatting so that the generated files are fractionally
    more readable
Changed param defaults for Microcosm
Added support for SPDY now that nginx 1.4 has arrived
Added back RC4 to mitigate BEAST attacks