document better different dependencies

this is written with recent Ubuntu and Debian in mind, but should be
working everywhere. the idea here is to make sure anyone can install
this without knowning too much about ACLs or anything similar.

closes #135

docs/global.rst.inc

@@ -9,6 +9,7 @@
 .. _HMAC-SHA256: http://en.wikipedia.org/wiki/HMAC
 .. _PBKDF2: https://en.wikipedia.org/wiki/PBKDF2
 .. _ACL: https://en.wikipedia.org/wiki/Access_control_list
+.. _libacl: http://savannah.nongnu.org/projects/acl/
 .. _github: https://github.com/jborg/attic
 .. _OpenSSL: https://www.openssl.org/
 .. _Python: http://www.python.org/

docs/installation.rst

@@ -12,6 +12,7 @@ Other dependencies:
 
 * `msgpack-python`_ >= 0.1.10
 * OpenSSL_ >= 1.0.0
+* libacl_
 
 The OpenSSL version bundled with Mac OS X and FreeBSD is most likey too old.
 Newer versions are available from homebrew_ on OS X and from FreeBSD ports.
@@ -19,11 +20,26 @@ Newer versions are available from homebrew_ on OS X and from FreeBSD ports.
 The llfuse_ python package is also required if you wish to mount an
 archive as a FUSE filesystem.
 
+Common compilation pre-requisites
+---------------------------------
+
+The following Debian packages are generally necessary to compile
+|project_name|, either through pip, the tarball or git::
+
+  $ sudo apt-get install python3 python3-dev python3-msgpack python3-sphinx libssl-dev libacl1-dev
+
 Installing from PyPI using pip
 ------------------------------
-::
 
-    $ pip install Attic
+To install |project_name| system-wide::
+
+  $ sudo pip3 install Attic
+
+To install it in a user-specific account::
+
+  $ pip3 install --user Attic
+
+Then add ``$HOME/.library/bin`` to your ``$PATH``.
 
 Installing from source tarballs
 -------------------------------
@@ -32,7 +48,7 @@ Installing from source tarballs
     $ curl -O :targz_url:`Attic`
     $ tar -xvzf |package_filename|
     $ cd |package_dirname|
-    $ python setup.py install
+    $ sudo python3 setup.py install
 
 Installing from git
 -------------------
@@ -40,7 +56,7 @@ Installing from git
 
     $ git clone |git_url|
     $ cd attic
-    $ python setup.py install
+    $ sudo python3 setup.py install
 
 Please note that when installing from git, Cython_ is required to generate some files that
 are normally bundled with the release tarball.