Add build instructions to readme file (#2290)

* Add build instructions to readme file

* Add npm install command to readme file

README.md

@@ -43,6 +43,31 @@ learn from other people doing development.
 
 [![Contributor Covenant](https://img.shields.io/badge/Contributor%20Covenant-v2.0%20adopted-ff69b4.svg)](CODE_OF_CONDUCT.md)
 
+### Running Mailspring from Source
+
+To install all dependencies and run Mailspring from its source code, 
+run the following commands from the root directory of the Mailspring repository:
+
+```
+npm install
+npm start
+```
+
+You can attach command line parameters by separating them using a double hyphen:
+
+```
+npm start -- --help
+```
+
+### Building Mailspring
+
+To build Mailspring, you need to run the following command from the root directory
+of the Mailspring repository:
+
+```
+npm run-script build
+```
+
 ### Building A Plugin
 
 Plugins lie at the heart of Mailspring and give it its powerful features.

app/build/README.md

@@ -1,24 +0,0 @@
-# N1 Build Environment
-Node version 0.10.x (Due to the version of electron currently used.)
-
-# N1 Building and Tasks
-
-This folder contains tasks to create production builds of N1
-
-Tasks should not be executed from this folder, but rather from `/scripts`. The
-`/scripts` folder has convenient methods that fix paths and do environment
-checks.
-
-Note that most of the task definitions are stored in `/build/tasks`
-
-## Some useful tasks
-
-NOTE: Run all of these from the N1 root folder.
-
-**Linting:**
-
-    `script/grunt lint`
-
-**Building:**
-
-    `script/grunt build`