Added General Usage Extractions to the README

Author: sijakubo

README.md

@@ -1,4 +1,4 @@
-Excel-Comparision Framework which is able to create a human readable diff when comparing Excel Files. 
+Excel-Comparision Framework which is able to create a human readable diff when comparing Excel Files. The Values are extracted using the `org.apache.poi` Framework  
 
 ## Integration 
 
@@ -15,20 +15,22 @@ dependencies {
 ### Maven
 ```
 <repositories>
-    <repository>
-      <id>jcenter</id>
-      <url>https://jcenter.bintray.com/</url>
-    </repository>
+  <repository>
+    <id>jcenter</id>
+    <url>https://jcenter.bintray.com/</url>
+  </repository>
 </repositories>
 ...
 <dependency>
-	<groupId>de.sijakubo</groupId>
-	<artifactId>excel-comparison</artifactId>
-	<version>0.1.1</version>
+  <groupId>de.sijakubo</groupId>
+  <artifactId>excel-comparison</artifactId>
+  <version>0.1.1</version>
 </dependency>
 ```
 
-## General Usage
+## General Usage Assertions
+
+To compare workbook / sheet content you can use the `ExcelAssert.java`. This provides methods to either compare Files or `org.apache.poi.ss.usermodel.Workbook` 
 
 ### JUnit
 ```java
@@ -59,3 +61,23 @@ public class ExcelComparisonTest {
       ExcelAssert.assertWorkbookEquals(actualWorkbook, expectedWorkbook)
   }
 ```
+
+## General Usage Extractions
+
+In order to compare the Content of an Excel file, i needed to extract the information to `basic` Java Types. 
+You can also use that to compare Excel Content as you like using the `ExcelExtractor.java`
+
+### Spock
+```groovy
+  //using spock  
+  def "should extract sheet containing formula"() {
+    given:
+      def testExcelFile = new File(this.getClass().getResource("formula_sample.xlsx").getFile())
+  
+      when:
+        List<Map<String, Object>> formularSheetValues = ExcelExtractor.extractSheetValues(testExcelFile, 0)
+  
+      then:
+        snapshot(formularSheetValues, JSON) == current(formularSheetValues, JSON)
+  }
+```