The use of a Java agent is now optional

Closes #27

README.md

@@ -37,7 +37,7 @@ on Java 7, in case the code accidentally uses Java 8 APIs or language features
 that Retrolambda doesn't backport.
 
 ```
-Usage: java -Dretrolambda.inputDir=? -Dretrolambda.classpath=? -javaagent:retrolambda.jar -jar retrolambda.jar
+Usage: java -Dretrolambda.inputDir=? -Dretrolambda.classpath=? [-javaagent:retrolambda.jar] -jar retrolambda.jar
 
 Retrolambda is a backporting tool for classes which use lambda expressions
 and have been compiled with Java 8, to run on Java 7 (maybe even Java 5).
@@ -70,6 +70,10 @@ Optional system properties:
       List of files to process, instead of processing all files.
       This is useful for a build tool to support incremental compilation.
 
+If the Java agent is used, then Retrolambda will use it to capture the
+lambda classes generated by Java. Otherwise Retrolambda will hook into
+Java's internal lambda dumping API, which is more susceptible to suddenly
+stopping to work between Java releases.
 ```
 
 
@@ -145,6 +149,14 @@ package-private.
 Version History
 ---------------
 
+### Upcoming
+
+- Does not anymore require the use of a Java agent
+  ([Issue #27](https://github.com/orfjackal/retrolambda/issues/27))
+- Maven plugin: by default run Retrolambda in the same process as Maven,
+  making it a bit faster. If Maven is not running under Java 8, then will
+  fall back to forking the process and using the Java agent mechanism
+
 ### Retrolambda 1.5.0 (2014-07-19)
 
 - Maven plugin: use the [JDK from Maven Toolchains](http://maven.apache.org/plugins/maven-toolchains-plugin/toolchains/jdk.html)

retrolambda/src/main/java/net/orfjackal/retrolambda/Config.java

@@ -148,7 +148,7 @@ public String getHelp() {
                 .map(key -> "-D" + key + "=?")
                 .reduce((a, b) -> a + " " + b)
                 .get();
-        return "Usage: java " + options + " -javaagent:retrolambda.jar -jar retrolambda.jar\n" +
+        return "Usage: java " + options + " [-javaagent:retrolambda.jar] -jar retrolambda.jar\n" +
                 "\n" +
                 "Retrolambda is a backporting tool for classes which use lambda expressions\n" +
                 "and have been compiled with Java 8, to run on Java 7 (maybe even Java 5).\n" +
@@ -164,7 +164,12 @@ public String getHelp() {
                 "\n" +
                 "Optional system properties:\n" +
                 "\n" +
-                optionalPropertiesHelp.stream().reduce((a, b) -> a + "\n" + b).get();
+                optionalPropertiesHelp.stream().reduce((a, b) -> a + "\n" + b).get() +
+                "\n" +
+                "If the Java agent is used, then Retrolambda will use it to capture the\n" +
+                "lambda classes generated by Java. Otherwise Retrolambda will hook into\n" +
+                "Java's internal lambda dumping API, which is more susceptible to suddenly\n" +
+                "stopping to work between Java releases.\n";
     }
 
     private static void requiredParameterHelp(String key, String... lines) {