Improve installation instructions in the docs (#483)

Update the `doc/install.rst` file by applying the same design used in
other of the Fatiando packages.

doc/install.rst

@@ -3,20 +3,48 @@
 Installing
 ==========
 
+There are different ways to install Harmonica:
+
+.. tab-set::
+
+ .. tab-item:: pip
+
+ Using the `pip package manager <https://pypi.org/project/pip/>`__:
+
+ .. code:: bash
+
+ pip install harmonica
+
+ .. tab-item:: conda/mamba
+
+ Using the `conda package manager <https://conda.io/>`__ (or ``mamba``)
+ that comes with the Anaconda/Miniconda distribution:
+
+ .. code:: bash
+
+ conda install harmonica --channel conda-forge
+
+ .. tab-item:: Development version
+
+ You can use ``pip`` to install the latest **unreleased** version from
+ GitHub (**not recommended** in most situations):
+
+ .. code:: bash
+
+ python -m pip install --upgrade git+https:/fatiando/harmonica
+
+.. note::
+
+ The commands above should be executed in a terminal. On Windows, use the
+ ``cmd.exe`` or the "Anaconda Prompt" app if you’re using Anaconda.
+
+
 Which Python?
 -------------
 
 You'll need **Python 3.8 or greater**.
 See :ref:`python-versions` if you require support for older versions.
 
-We recommend using the
-`Anaconda Python distribution <https://www.anaconda.com/download>`__
-to ensure you have all dependencies installed and the ``conda`` package manager
-available.
-Installing Anaconda does not require administrative rights to your computer and
-doesn't interfere with any other Python installations in your system.
-
-
 Dependencies
 ------------
 
@@ -58,40 +86,6 @@ The examples in the :ref:`gallery` also use:
 * `pyproj <https://jswhit.github.io/pyproj/>`__ for cartographic projections
 
 
-
-Installing with conda
----------------------
-
-You can install Harmonica using the `conda package manager
-<https://conda.io/>`__ that comes with the Anaconda distribution::
-
- conda install harmonica --channel conda-forge
-
-
-Installing with pip
--------------------
-
-Alternatively, you can also use the `pip package manager
-<https://pypi.org/project/pip/>`__::
-
- pip install harmonica
-
-
-Installing the latest development version
------------------------------------------
-
-You can use ``pip`` to install the latest source from Github::
-
- pip install git+https:/fatiando/harmonica
-
-Alternatively, you can clone the git repository locally and install from
-there::
-
- git clone https:/fatiando/harmonica.git
- cd harmonica
- pip install .
-
-
 Testing your install
 --------------------