Completely overhaul the documentation

readthedocs/basic/installation.rst

@@ -0,0 +1,77 @@
+.. _installation:
+
+============
+Installation
+============
+
+Telethon is a Python library, which means you need to download and install
+Python from https://www.python.org/downloads/ if you haven't already. Once
+you have Python installed, run:
+
+.. code-block:: sh
+
+    pip3 install -U telethon --user
+
+To install or upgrade the library to the latest version.
+
+
+Installing Development Versions
+===============================
+
+If you want the *latest* unreleased changes,
+you can run the following command instead:
+
+.. code-block:: sh
+
+    pip3 install -U https://github.com/LonamiWebs/Telethon/archive/master.zip --user
+
+.. note::
+
+    The development version may have bugs and is not recommended for production
+    use. However, when you are `reporting a library bug`__, you should try if the
+    bug still occurs in this version.
+
+.. __: https://github.com/LonamiWebs/Telethon/issues/
+
+
+Verification
+============
+
+To verify that the library is installed correctly, run the following command:
+
+.. code-block:: sh
+
+    python3 -c 'import telethon; print(telethon.__version__)'
+
+The version number of the library should show in the output.
+
+
+Optional Dependencies
+=====================
+
+If cryptg_ is installed, **the library will work a lot faster**, since
+encryption and decryption will be made in C instead of Python. If your
+code deals with a lot of updates or you are downloading/uploading a lot
+of files, you will notice a considerable speed-up (from a hundred kilobytes
+per second to several megabytes per second, if your connection allows it).
+If it's not installed, pyaes_ will be used (which is pure Python, so it's
+much slower).
+
+If pillow_ is installed, large images will be automatically resized when
+sending photos to prevent Telegram from failing with "invalid image".
+Official clients also do this.
+
+If aiohttp_ is installed, the library will be able to download
+:tl:`WebDocument` media files (otherwise you will get an error).
+
+If hachoir_ is installed, it will be used to extract metadata from files
+when sending documents. Telegram uses this information to show the song's
+performer, artist, title, duration, and for videos too (including size).
+Otherwise, they will default to empty values, and you can set the attributes
+manually.
+
+.. _cryptg: https://github.com/Lonami/cryptg
+.. _pyaes: https://github.com/ricmoo/pyaes
+.. _pillow: https://python-pillow.org
+.. _aiohttp: https://docs.aiohttp.org
+.. _hachoir: https://hachoir.readthedocs.io