several small documentation fixes

INSTALL

@@ -28,7 +28,7 @@ The following software is highly recommended though not strictly required:
 Generic instructions
 ====================
 
-Please note the `System-specific instructions`_ below.
+Please note the `system-specific instructions`_ below.
 
 kwant can be built and installed following the `usual Python conventions
 <http://docs.python.org/install/index.html>`_ by running the following commands

doc/source/tutorial/tutorial2.rst

@@ -116,7 +116,7 @@ the following, clearly non-monotonic conductance steps:
     `~kwant.builder.Builder.possible_hoppings` is given in terms of
     lattice indices, i.e. relative to the Bravais lattice vectors.
     For a square lattice, the Bravais lattice vectors are simply
-    :math:`(a,0)` and :math:`(0,a)`, and hence the mapping from
+    `(a,0)` and `(0,a)`, and hence the mapping from
     lattice indices `(i,j)` to real space and back is trivial.
     This becomes more involved in more complicated lattices, where
     the real-space directions corresponding to, for example, `(1,0)`

doc/source/whatsnew/0.2.rst

@@ -31,12 +31,12 @@ New tutorial dealing with superconductivity
 
 New `~kwant.plotter` module
 ---------------------------
-`~kwant.plotter` has been rewritten using `matplotlib`, which allows
+`~kwant.plotter` has been rewritten using matplotlib, which allows
 plot post-processing, basic 3D plotting and many other features. Due to the
-possibility to easily modify a `matplotlib` plot after it has been generated,
+possibility to easily modify a matplotlib plot after it has been generated,
 function `~kwant.plotter.plot` has much fewer input parameters, and is less
 flexible than its previous implementation. Its interface is also much more
-similar to that of `matplotlib`. For the detailed interface and input
+similar to that of matplotlib. For the detailed interface and input
 description check `~kwant.plotter.plot` documentation.
 
 The behavior of `~kwant.plotter.plot` with low level systems has changed.