Update Readme

Merge the two Installation section
Remove the old example and put new ones

README.rst

@@ -1,62 +1,93 @@
 pylas
 -----
 
-Another way of reading LAS/LAZ in Python.
+Another way of reading point clouds in the LAS/LAZ in Python.
 
 .. image:: https://readthedocs.org/projects/pylas/badge/?version=latest
     :target: https://pylas.readthedocs.io/en/latest/?badge=latest
     :alt: Documentation Status
 
-
 .. image:: https://travis-ci.org/tmontaigu/pylas.svg?branch=master
 
 
-Example
--------
+Examples
+--------
+
+Directly read and write las
 
 .. code:: python
 
     import pylas
 
-    # Directly read and write las 
     las = pylas.read('filename.las')
-    las = pylas.convert(las, point_format_id=2)
-    las.write('converted.las')
+    las.points = las.points[las.classification == 2]
+    las.write('ground.laz')
+
+Open data to inspect header (opening only reads the header and vlrs)
+
+.. code:: python
+
+    import pylas
 
-    # Open data to inspect header and then read
     with pylas.open('filename.las') as f:
-        if f.header.point_count < 10 ** 8:
-            las = f.read()
-    print(las.vlrs)
+        print(f"Point format:       {f.header.point_format}")
+        print(f"Number of points:   {f.header.point_count}")
+        print(f"Number of vlrs:     {len(f.header.vlrs)}")
 
-Documentation is hosted on ReadTheDocs_ .
+Use the 'chunked' reading & writing features
 
-.. _ReadTheDocs: http://pylas.readthedocs.io/en/latest/index.html
+.. code:: python
 
+    import pylas
 
-Installation
-------------
+    with pylas.open('big.laz') as input_las:
+        with pylas.open('ground.laz', mode="w", header=input_las.header) as ground_las:
+            for points in input_las.chunk_iterator(2_000_000):
+                ground_las.write_points(points[points.classification == 2])
 
-See the Installation_ section of the documentation:
+Appending points to existing file
+
+.. code:: python
+
+    import pylas
+
+    with pylas.open('big.laz') as input_las:
+        with pylas.open('ground.laz', mode="a") as ground_las:
+            for points in input_las.chunk_iterator(2_000_000):
+                ground_las.append_points(points[points.classification == 2])
+
+Documentation
+-------------
+
+Documentation is hosted on ReadTheDocs_ .
+
+.. _ReadTheDocs: http://pylas.readthedocs.io/en/latest/index.html
 
-.. _Installation: https://pylas.readthedocs.io/en/latest/installation.html
 
 Dependencies & Requirements
 ---------------------------
 
 Supported CPython versions are: 3.6, 3.7, 3.8, 3.9
 
-pylas supports LAS natively,to support LAZ it needs one of its supported backend to be installed:
+pylas supports LAS natively, to support LAZ it needs one of its supported backend to be installed:
 
- - lazrs
- - laszip
+- lazrs
+- laszip
 
 
 Installation
 ------------
 
-::
+.. code-block:: shell
 
-    pip install pylas
+    pip install pylas # without LAZ support
+    # Or
+    pip install pylas[laszip] # without LAZ support via LASzip
+    # Or
+    pip install pylas[lazrs] # without LAZ support via lazrs
 
 
+See the Installation_ section of the documentation for details:
+
+.. _Installation: https://pylas.readthedocs.io/en/latest/installation.html
+