Re-packaged with setuptools for standard installation

* 'python setup.py install' will install
  - a package 'propka' (which contains everything that 'Source' contained
    in the original distribution)
  - an executable script 'propka31' (which is identical to the original
    'propka.py' script but it is automatically generated via the setuptools
    mechanism; it uses propka.run.main().
* 'pip install' will also work
* the README.md file was changed to reflect the alterations
* metadata in the setup.py file was added

NOTE: The licence is still unclear!

propka/run.py

@@ -0,0 +1,15 @@
+# entry point for propka script
+
+import propka.lib, propka.molecular_container
+
+def main():
+    """
+    Reads in structure files, calculates pKa values, and prints pKa files
+    """
+    # loading options, flaggs and arguments
+    options, pdbfiles = propka.lib.loadOptions()
+
+    for pdbfile in pdbfiles:
+        my_molecule = propka.molecular_container.Molecular_container(pdbfile, options)
+        my_molecule.calculate_pka()
+        my_molecule.write_pka()