docs: fix code blocks in installation.rst

In one case removed the |project_name| and |git_url| variables to fix
the display of the code block. Shouldn't be problematic, as they are not
used consistently in this document anyway.

Put two notes in their own nice '.. note::' blocks.

docs/installation.rst

@@ -91,7 +91,7 @@ Check https://github.com/borgbackup/borg/releases for available binaries.
 Debian Jessie / Ubuntu 14.04 preparations (git/pypi)
 ----------------------------------------------------
 
-.. parsed-literal::
+::
 
     # Python 3.x (>= 3.2) + Headers, Py Package Installer, VirtualEnv
     apt-get install python3 python3-dev python3-pip python-virtualenv
@@ -121,7 +121,7 @@ Debian Jessie / Ubuntu 14.04 preparations (git/pypi)
 Korora / Fedora 21 preparations (git/pypi)
 ------------------------------------------
 
-.. parsed-literal::
+::
 
     # Python 3.x (>= 3.2) + Headers, Py Package Installer, VirtualEnv
     sudo dnf install python3 python3-devel python3-pip python3-virtualenv
@@ -178,9 +178,7 @@ In case that creation of the virtual env fails, try deleting this file:
 Installation (pypi)
 -------------------
 
-This uses the latest (source package) release from PyPi.
-
-.. parsed-literal::
+This uses the latest (source package) release from PyPi. ::
 
     virtualenv --python=python3 borg-env
     source borg-env/bin/activate   # always before using!
@@ -190,19 +188,17 @@ This uses the latest (source package) release from PyPi.
                                # 0.41 and 0.41.1 have unicode issues at install time
     pip install borgbackup
 
-Note: we install into a virtual environment here, but this is not a requirement.
+.. note:: We install into a virtual environment here, but this is not a requirement.
 
 
 Installation (git)
 ------------------
 
 This uses latest, unreleased development code from git.
-While we try not to break master, there are no guarantees on anything.
-
-.. parsed-literal::
+While we try not to break master, there are no guarantees on anything. ::
 
-    # get |project_name| from github, install it
-    git clone |git_url|
+    # get borg from github
+    git clone https://github.com/borgbackup/borg.git
 
     virtualenv --python=python3 borg-env
     source borg-env/bin/activate   # always before using!
@@ -218,4 +214,4 @@ While we try not to break master, there are no guarantees on anything.
     # optional: run all the tests, on all supported Python versions
     fakeroot -u tox
 
-Note: as a developer or power user, you always want to use a virtual environment.
+.. note:: As a developer or power user, you always want to use a virtual environment.