Made bin/www executable
Added config.json.dist file

The username and password of the account used should be stored in
config.json file. config.json.dist file is added to help users in
creating this file. They can rename the file to config.json

config.json file differs from user to user and should not be
version tracked.
Added a mailer module to wrap node mailer transporter

This should make the code easier to test.
Added a (incomplete) test for '/' post action

It is expected that these tests will be completed in following commits.
Added npm-debug.log to gitignore