Add plantuml layer

Adds support for PlanetUML, a tool to generate
UML diagrams from plain text.

layers/+lang/plantuml/README.org

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+#+TITLE: plantuml layer
+#+HTML_HEAD_EXTRA: <link rel="stylesheet" type="text/css" href="../../css/readtheorg.css" />
+[[file:img/logo.png]]
+* Table of Contents                                        :TOC_4_org:noexport:
+ - [[Description][Description]]
+ - [[Install][Install]]
+ - [[Key bindings][Key bindings]]
+
+* Description
+This layer enables support for [[https://github.com/skuro/puml-mode][puml-mode]], which provides
+a major-mode for [[http://plantuml.com][plantuml]]. PlantUML is a tool to generate [[https://en.wikipedia.org/wiki/Unified_Modeling_Language][UML diagrams]] from plain-text.
+
+For help with how to use plantuml, see the [[http://plantuml.com][plantuml website]] and the [[http://plantuml.com/PlantUML_Language_Reference_Guide.pdf][reference guide]].
+
+The official file extension supported by this layer is =.pum=. If you want something else,
+set it in your =user-config= function of your =~/.spacemacs= file.
+
+For example, the following diagram can be defined as follows:
+
+#+BEGIN_SRC plantuml
+@startuml
+JAremko->robbyoconnor : I think the docs can benefit from some kind of illustration
+JAremko<-robbyoconnor : I'm too lazy -- I have actual work to do. I link to the docs. If you can write me a diagram in plantuml, I'll gladly compile and add it.
+JAremko->robbyoconnor : *gives ths diagram*
+robbyoconnor<-JAremko : *robbyoconnor adds it and JAremko is happy*
+...
+robbyoconnor->theOtherPerson : And they thinks it's funny? Yup, they definitely finds it funny. Right?
+@enduml
+#+END_SRC
+
+[[file:img/dia.png]]
+
+
+
+* Install
+To use this contribution add it to your =~/.spacemacs=
+
+#+begin_src emacs-lisp
+  (setq-default dotspacemacs-configuration-layers '(plantuml))
+#+end_src
+
+* Key bindings
+
+| Key Binding              | Description                                           |
+|--------------------------+-------------------------------------------------------|
+| ~SPC m c c~ or ~C-c C-c~ | Build diagram from the text in the current buffer     |
+| ~SPC m c o~              | Set the output type (~unicode text~, ~svg~, or ~png~) |

layers/+lang/plantuml/packages-config.el

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+;;; packages-config.el --- plantuml layer packages file for Spacemacs.
+;;
+;; Copyright (c) 2012-2016 Sylvain Benner & Contributors
+;;
+;; Author: Robert O'Connor <robby.oconnor@gmail.com>
+;; URL: https://github.com/robbyoconnor
+;;
+;; This file is not part of GNU Emacs.
+;;
+;;; License: GPLv3
+
+;;; Commentary:
+
+;;; Code:
+
+(defconst plantuml-packages
+  '(puml-mode))
+
+;;; packages-config.el ends here

layers/+lang/plantuml/packages.el

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+;;; packages.el --- plantuml layer packages file for Spacemacs.
+;;
+;; Copyright (c) 2012-2016 Sylvain Benner & Contributors
+;;
+;; Author: Robert O'Connor <robby.oconnor@gmail.com>
+;; URL: https://github.com/robbyoconnor
+;;
+;; This file is not part of GNU Emacs.
+;;
+;;; License: GPLv3
+
+;;; Commentary:
+
+;;; Code:
+
+(defun plantuml/init-puml-mode ()
+  (use-package puml-mode
+    :defer t
+    :mode ("\\.pum$" . puml-mode)
+
+    :config (spacemacs/set-leader-keys-for-major-mode 'puml-mode
+              "cc" 'puml-preview
+              "co" 'puml-set-output-type)))
+;;; packages.el ends here