Hidden files are ignored. Added --version option and logging.

* Added logging with SLF4J and Logback
* Added `--version` option.
* Mofidied the input file rules. When an input object is a directory, JLPMain is
  adding all the files in that directory and its subdirectories. Now JLPMain is
  ignoring hidden files in the directory and subdirs. A file named explicitly on
  the command line is still included regardless of if it is hidden or not.
* Documentation continues.

resources/main/logback.groovy

@@ -0,0 +1,17 @@
+import ch.qos.logback.classic.encoder.PatternLayoutEncoder
+import ch.qos.logback.core.ConsoleAppender
+import ch.qos.logback.core.FileAppender
+
+import static ch.qos.logback.classic.Level.*
+
+appender("stdout", ConsoleAppender) {
+    encoder(PatternLayoutEncoder) {
+        pattern = "%level %msg%n" }}
+
+appender("logfile", FileAppender) {
+    file = "jlp.log" 
+    encoder(PatternLayoutEncoder) {
+        pattern = "%date %level %logger{10} [%file:%line] %msg%n" }}
+
+root(WARN, ["stdout"])
+//logger("com.jdblabs.jlp", TRACE, ["file"])