Update README

Add example

README.md

@@ -1,5 +1,68 @@
-A portable, simple zip library written in C
+A portable (OSX/Linux/Windows), simple zip library written in C
 ===========================================
 <img src="zip.png" name="zip" />
 This is done by hacking awesome [miniz](https://code.google.com/p/miniz) library and layering functions on top of the miniz v1.15 API.
 
+# The Idea 
+... Some day, I was looking for zip library written in C for my project, but I could not find anything simple enough and lightweight.
+Everything what I tried required 'crazy mental gymnastics' to integrate or had some limitations or was too heavy. 
+I hate frameworks, factories and adding new dependencies. If I must to install all those dependencies and link new library, I'm getting almost sick. 
+I wanted something powerfull and small enough, so I could add just a few files and compile them into my project. 
+And finally I found miniz. 
+Miniz is a lossless, high performance data compression library in a single source file. I only needed simple interface to append buffers or files to the current zip-entry. Thanks to this feature I'm able to merge many files/buffers and compress them on-the-fly.
+
+It was the reason, why I decided to write zip module on top of the miniz. It required a little bit hacking and wrapping some functions, but I kept simplicity. So, you grab these 3 files and compile it into your project. I hope that interface is also extremely simple, so you will not have any problems to understand it.
+
+# Example
+
+```c
+#include <stdio.h>
+#include <string.h>
+
+#include "zip.h"
+
+// callback function
+int on_extract_entry(const char *filename, void *arg) {
+	static int i = 0;
+	int n = *(int *)arg;
+	printf("Extracted: %s (%d of %d)\n", filename, ++i, n);	
+
+	return 0;
+}
+
+int main() {
+	/* 
+	   Create a new zip archive with default compression level (6)	   
+	*/
+	struct zip_t *zip = zip_open("foo.zip", ZIP_DEFAULT_COMPRESSION_LEVEL, 0);
+	// we should check if zip is NULL
+	{
+		zip_entry_open(zip, "foo-1.txt");
+		{
+			char *buf = "Some data here...";
+			zip_entry_write(zip, buf, strlen(buf));
+		}
+		zip_entry_close(zip);
+
+		zip_entry_open(zip, "foo-2.txt");
+		{
+			// merge 3 files into one entry and compress them on-the-fly.
+			zip_entry_fwrite(zip, "foo-2.1.txt");
+			zip_entry_fwrite(zip, "foo-2.2.txt");
+			zip_entry_fwrite(zip, "foo-2.3.txt");
+		}
+		zip_entry_close(zip);		
+	}
+	// always remember to close and release resources
+	zip_close(zip);
+		
+
+	/*
+		Extract a zip archive into /tmp folder
+	*/
+	int arg = 2;
+	zip_extract("foo.zip", "/tmp", on_extract_entry, &arg);
+
+	return 0;
+}
+```