add Maven exec example to readme

Author: axkr

README.md

@@ -1 +1,9 @@
 Very experimental prototype for transpiling [SymPy math expressions (Python)](https://github.com/sympy/sympy) into [Symja math expressions (Java)](https://github.com/axkr/symja_android_library).
+
+With the following Maven command you can run the **SymPy2Symja console** from the command line
+
+```
+mvn exec:java@sympy2symja
+```
+
+<img src="https://raw.githubusercontent.com/axkr/sympy2symja/master/sympy2symja.png" width="100%"></img> 

SympyToSymja/pom.xml

@@ -48,7 +48,7 @@
 	</properties>
 	<dependencies>
 		<dependency>
-			<groupId>org.matheclipse</groupId> 
+			<groupId>org.matheclipse</groupId>
 			<artifactId>matheclipse-core</artifactId>
 			<version>3.1.0-SNAPSHOT</version>
 		</dependency>
@@ -76,4 +76,27 @@
 			<version>4.7.1</version>
 		</dependency>
 	</dependencies>
+	<build>
+		<pluginManagement>
+			<plugins>
+				<plugin>
+					<groupId>org.codehaus.mojo</groupId>
+					<artifactId>exec-maven-plugin</artifactId>
+					<version>3.2.0</version>
+					<executions>
+						<execution>
+							<id>sympy2symja</id>
+							<goals>
+								<goal>java</goal>
+							</goals>
+							<configuration>
+								<mainClass>
+									org.matheclipse.core.sympy2symja.SympyToSymjaExpr</mainClass>
+							</configuration>
+						</execution>
+					</executions>
+				</plugin>
+			</plugins>
+		</pluginManagement>
+	</build>
 </project>

SympyToSymja/src/main/java/org/matheclipse/core/sympy2symja/SympyToSymjaExpr.java

@@ -1,7 +1,6 @@
 package org.matheclipse.core.sympy2symja;
 
 import java.io.BufferedReader;
-import java.io.File;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.nio.charset.StandardCharsets;
@@ -47,9 +46,6 @@ public static void main(String[] args) throws Exception {
     System.out.println(
         "Create a Symja Java string from the SymPy expression input");
     F.initSymbols();
-    String userHome = System.getProperty("user.home");
-    File sourceLocation =
-        new File(userHome + "/git/symja_android_library/symja_android_library/doc/functions");
     String inputExpression;
     String trimmedInput;
     while (true) {