Added a docs section on Linux installation
This simply adds a short paragraph on what dependencies are needed on
Linux, as well as the command line to install them on Ubuntu (since
users of other distributions are more likely to know how to do it).
diff --git a/docs/installation.rst b/docs/installation.rst
index 7e7348e..a2fc5b7 100644
--- a/docs/installation.rst
+++ b/docs/installation.rst
@@ -22,8 +22,26 @@
C:\> set INCLUDE=C:\OpenSSL-1.0.1f-64bit\include;%INCLUDE%
C:\> pip install cryptography
+Building cryptography on Linux
+------------------------------
+
+``cryptography`` should build very easily on linux provided you have headers
+for the OpenSSL and libffi available on your system.
+
+For Ubuntu, the following command line will ensure this is the case:
+
+.. code-block:: console
+
+ sudo apt-get install libssl-dev libffi-dev
+
+You should now be able to build and install cryptography with the usual
+
+.. code-block:: console
+
+ python setup.py install
+
Using your own OpenSSL on Linux
--------------------------------
+...............................
Python links to OpenSSL for its own purposes and this can sometimes cause
problems when you wish to use a different version of OpenSSL with cryptography.