updated docs

docs/quickstart.rst

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+Quickstart
+==========
+
+Install blag from PyPI_::
+
+    $ pip install blag
+
+.. _pypi: https://pypi.org/project/blag/
+
+Run blag's quickstart command to create the configuration needed::
+
+    $ blag quickstart
+
+Create some content::
+
+    $ mkdir content
+    $ edit content/hello-world.md
+
+Generate the website::
+
+    $ blag build
+
+By default, blag will search for content in ``content`` and the output will be
+generated in ``build``. Those directories can be changed via command line
+arguments. See::
+
+    $ blag --help
+
+