requirements: Drop some optional requirements

Move some non pure python requirements (namely lxml and paramiko)
from pip-requires to test-requires.  Document it in README.rst.

Motivations:

- Make this pip-installable with pypy
- Less distribution package requirements (deb/rpm/etc) in case
  a user do not actually need the functionality

Note: while paramiko itself is pure python, it requires pycrypto.
Note: msgpack has pure python fallback implementation.

Separating ryu into smaller packages would be a better alternative.
However, it would involve a lot more work than this workaround.

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

README.rst

@@ -33,6 +33,21 @@ After writing your application, just type::
    % ryu-manager yourapp.py
 
 
+Optional Requirements
+=====================
+
+Some functionalities of ryu requires extra packages:
+
+- OF-Config requires lxml
+- NETCONF requires paramiko
+- BGP speaker (net_cntl) requires paramiko
+
+If you want to use the functionalities, please install requirements::
+
+    % pip install lxml
+    % pip install paramiko
+
+
 Support
 =======
 Ryu Official site is `<http://osrg.github.io/ryu/>`_.

tools/pip-requires

@@ -1,9 +1,7 @@
 eventlet
-lxml  # OF-Config
 msgpack-python>=0.3.0  # RPC library, BGP speaker(net_cntl)
 netaddr
 oslo.config>=1.2.0
-paramiko  # NETCONF, BGP speaker
 routes  # wsgi
 six>=1.4.0
 webob>=1.2  # wsgi

tools/test-requires

@@ -4,3 +4,5 @@ nose
 pep8
 pylint==0.25.0
 xml_compare
+lxml  # OF-Config
+paramiko  # NETCONF, BGP speaker