Mailhog

* Download message in .eml format
* Cleaned up v1 API
* Web UI and API improvements
* Fixed UI rendering bugs
* Message search and matched/total message count
* Message list resizing and scrolling
* EventSource support for message streaming
* Better error handling and reporting
* View/download individual MIME parts
* Release messages to real SMTP servers
* Switch to [go-bindata](https://github.com/jteeuwen/go-bindata) for asset embedding

- Update .travis.yml to Go 1.6 and tip
- Fix builds broken by out of date mgo import path
- 82 - fix configuration documentation, thanks riking
- 83 - add search query parameter to Swagger JSON, thanks kkrauth
- 86 - vendor all dependencies
- 89 - add missing iso88591_map.js and sjis_map.js
- 90 - update broken link in documentation, thanks espen
- 91 - add assets/js/filesize-3.1.2.min.js
- 93 - starting MailHog as a service using brew, thanks espen
- 95 - fix UTF-8 encoding bug in attachment names
- 97 - fix header case sensitivity bug
- 102 - merge multiple PRs adding WebSocket support, thanks GREsau
- mailhog/smtp2 - use file modification time for Created field, thanks esiqveland

* Better support for ESMTP (RFC5321)
* Support for SMTP AUTH (RFC4954) and PIPELINING (RFC2920)
* Improved AJAX web interface to view messages (plain text, HTML or source)
* Improved HTTP API to list, retrieve and delete messages
* Multipart MIME support
* In-memory message storage
* MongoDB storage for message persistence

- mailhog/storage1 - fix MongoDB storage bug, and implement search, thanks HokieTT
- 13 - implement file based storage backend (currently without search)

- 76 - optimise docker image size, thanks missedone
- 77 - fix ci by removing go-uuid, thanks missedone
- 80, mailhog/MailHog-UI15, mailhog/MailHog-Server2 - add webpath, thanks oers
- mailhog/MailHog-UI13 - create hyperlinks for URLs in plain text, thanks GREsau
- mailhog/MailHog-UI14 - add no-referrer referrer policy, thanks djmattyg007

- Add `MailHog sendmail` shortcut to `mhsendmail`
- Add 40 - HTTP basic authentication
- Add 63 - message size in UI
- Fix mailhog/MailHog-UI10 - fix delete for in-memory storage
- Merge mailhog/MailHog-UI8 - fix styles for .content positioning, thanks thejameskyle
- Merge mailhog/MailHog-UI9 - fix content types, thanks danielwhite
- Merge mailhog/data4 - factor out use of log package, thanks ishbir