setup: add SRP as dependency in the library setup.py file

- This will make the library to download and install the SRP module dependency
  automatically when installing the library from PyPI.

Signed-off-by: Diego Escalona <diego.escalona@digi.com>

Author: diescalo

setup.py

@@ -11,6 +11,7 @@
 
 DEPENDENCIES = (
     'pyserial>=3',
+    'srp',
 )
 
 here = path.abspath(path.dirname(__file__))
@@ -32,6 +33,7 @@
     python_requires='>=3',
     install_requires=[
         'pyserial>=3',
+        'srp',
     ],
     classifiers=[
         'Development Status :: 5 - Production/Stable',