Add copyright notice to LICENSE, update README

Add copyright notice before GPLv3 license.

Version v1.0.3 cannot be built on Flutter v1.17+ due to outdated
dependencies. The README has been updated highlighting the issue.

More info at: #23

LICENSE

@@ -1,3 +1,22 @@
+Soif - An application to monitor and display soil moisture content for drip 
+irrigation.
+    Copyright (C) 2019, 2020 Anurag Roy, Aritra Roy Gosthipaty
+
+    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 of the License, 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.  If not, see <https://www.gnu.org/licenses/>.                    
+
+=============================================================================
+
                     GNU GENERAL PUBLIC LICENSE
                        Version 3, 29 June 2007
 

README.md

@@ -8,6 +8,12 @@ Color Theme: [Material.io](https://material.io/resources/color/#!/?view.left=0&v
 
 Font: [OCRB](https://github.com/opensourcedesign/fonts/tree/master/OCR)
 
+### IMPORTANT: Read this first
+
+The codebase hosted in this branch _will not build_ on **Flutter v1.17+** due to [outdated dependencies](https://github.com/RoyARG02/soil_moisture_app/issues/23).
+
+If you are still interested in this version, consider using any of the pre-built binaries on the [releases](https://github.com/RoyARG02/soil_moisture_app/releases) page.
+
 ### Screenshots
 
 <p align = "middle">