Add compilation guide, and spell checking feature

README.md

@@ -31,6 +31,7 @@ Features
 - *obtaining installed packages*
 - *generating PDF files*
 - *preview generated PDF files*
+- *spell checking*
 - *and more...*
 
 
@@ -44,6 +45,13 @@ Installation
 
 Restart IDE.
 
+Build from source:
+
+1. [Check out the source of IntelliJ IDEA Community Edition](http://www.jetbrains.org/intellij/sdk/docs/basics/checkout_and_build_community.html), no need to build it.
+1. [Configure IntelliJ Platform SDK for this project](http://www.jetbrains.org/intellij/sdk/docs/basics/getting_started/setting_up_environment.html#configuring-intellij-platform-sdk);
+1. Deploy the plugin: under project root, run `./gradlew build`;
+1. Plugin release is under `build/distributions`, which can be installed via IntelliJ;
+
 
 Usage
 -----