Some modification (see extended description)

.gitignore : Made some modifications, for git to ignore vim files and
node modules.
app.js : modified routes.
package.json : modified project name.
routes\user.js : added get_login and post_login prototype.
routes\conversation.js : added list, get_new, and post_new prototype.
routes\index.js : was useless here, conversation.list acts as the index.