Change "Select Files" label to "Attach Files"

Fixes #111
Filter out tag/E-Mail account from user permission array that are later removed
Showing time (in ago) when reply was posted
Sending attachments literally rather than just sending its link in E-Mail

Currently it was sending a link to attachment hosted in our site. This was
a problem esp. for sites that are not publiciy accessible
Merge pull request #115 from VarunAgw/notifications

Restrict notifications to tags/accounts the user is authorized to view.
Merge pull request #121 from VarunAgw/cron

Ensure messages are archived correctly after processing.
Merge pull request #125 from VarunAgw/attachments

Attach files to messages instead of sending links.
Merge pull request #124 from VarunAgw/ui-ux

Change "Select Files" label to "Attach Files"
Redesign details meta box

This new one looks much similar to WP post meta box
Moved E-Mail account dropdown to top
Declaring variables in local scope

Currently variables are declared in global scope rather than local scope.
They are not required globally.
Merge pull request #122 from VarunAgw/meta-box-details

Redesign Details metabox to be more visually consistent with Core.
Using a class rather than ID to get save button
Showing permissions filter using tables
Renamed SupportFlow_Email_Accounts class reference
Create get_email_accounts() to get E-Mail accounts array
Using SupportFlow_Email_Accounts::get_email_accounts() to get array of E-Mail accounts

Currently it is accessing them directly from database
Creted SupportFlow_Permissions::get_user_permisssions() to get array of user allowed tag/E-Mail account
Using SupportFlow_Permissions::get_user_permissions_data() to get permissions for a user

Earlier code was directly querying it from database
Created SupportFlow_Email_Notifications::get_email_notifications() to get tag/E-Mail account user opted to receive E-Mail notifications