Use GPL 3 for lsp-ui.el

The file was initially created as a placeholder for UI stuff by topisani.
Sebastien Chapuis contributed most components and I polished them and touched most lines in this particular file.

Move away from the confusing mix of GPL 3 and MIT. This was agreed by topisani: #73 (comment)

LICENSE

@@ -1,27 +1,3 @@
-The file lsp-ui.el is released under the following license:
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in
-all copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
-
-----------------------------------------------------------------------
-
-The other files are released under the following license:
-
                     GNU GENERAL PUBLIC LICENSE
                        Version 3, 29 June 2007
 
@@ -695,4 +671,4 @@ into proprietary programs.  If your program is a subroutine library, you
 may consider it more useful to permit linking proprietary applications with
 the library.  If this is what you want to do, use the GNU Lesser General
 Public License instead of this License.  But first, please read
-<http://www.gnu.org/philosophy/why-not-lgpl.html>.
+<http://www.gnu.org/philosophy/why-not-lgpl.html>.

lsp-ui.el

@@ -1,30 +1,30 @@
 ;;; lsp-ui.el --- UI modules for lsp-mode            -*- lexical-binding: t; -*-
 
 ;; Copyright (C) 2017 Tobias Pisani
+;; Copyright (C) 2018 Sebastien Chapuis, Fangrui Song
 
-;; Author:  Tobias Pisani <[email protected]>
+;; Author: Sebastien Chapuis <[email protected]>, Fangrui Song <[email protected]>
 ;; Keywords: lsp
 ;; URL: https://github.com/emacs-lsp/lsp-ui
 ;; Package-Requires: ((emacs "25.1") (dash "2.14") (dash-functional "1.2.0") (flycheck "31") (lsp-mode "4.2") (markdown-mode "2.3"))
 ;; Version: 0.0.1
 
-;; Permission is hereby granted, free of charge, to any person obtaining a copy
-;; of this software and associated documentation files (the "Software"), to deal
-;; in the Software without restriction, including without limitation the rights
-;; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-;; copies of the Software, and to permit persons to whom the Software is
-;; furnished to do so, subject to the following conditions:
-
-;; The above copyright notice and this permission notice shall be included in
-;; all copies or substantial portions of the Software.
-
-;; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-;; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-;; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-;; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-;; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-;; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-;; SOFTWARE.
+;;; License
+;;
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 3, or (at your option)
+;; any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program; see the file COPYING.  If not, write to
+;; the Free Software Foundation, Inc., 51 Franklin Street, Fifth
+;; Floor, Boston, MA 02110-1301, USA.
 
 ;;; Commentary: