Break up docs

docs/examples.rst

+Examples
+========
+
+Setup
+-----
+
+>>> import csppfetch
+>>> import datetime
+>>> sst_filename = "avhrr-only-v2.%Y%m%d_preliminary.nc"
+>>> sst = csppfetch.Downloader(
+...     name = "Sea Surface Temperature",
+...     package_env_id = 'CSPP_GEO_AITF_',
+...     url_base = "https://geodb.ssec.wisc.edu/ancillary/",
+...     url_relative = "%Y_%m_%d_%j/"+sst_filename,
+...     local = sst_filename,
+...     period = datetime.timedelta(hours=24),
+...     epoch_start = datetime.datetime(2010,1,1,3,0,0)
+...     )
+
+(These imports are for these examples. They're not required to use the module!)
+ 
+>>> from tempfile import TemporaryDirectory
+>>> import os
+
+
+Download For Time
+-----------------
+
+Download files needed to process a scan at 2019-5-27 12:00:00:
+
+>>> scan_time = datetime.datetime(2019,5,27, 12,0,0)
+>>> with TemporaryDirectory() as example_dir:
+...     sst.download_for_time(scan_time, example_dir)
+...     os.path.exists(example_dir+"/avhrr-only-v2.20190527_preliminary.nc")
+True
+
+Create/Maintain Local Cache
+---------------------------
+
+Download last 7 days of files
+
+>>> with TemporaryDirectory() as example_dir:
+...     sst.mirror(example_dir)
+...     len(os.listdir(example_dir)) > 3
+True
+
+(The number of files is compared to 3 because due to vaguaries of creation and
+mirroring, we are likely to get fewer, sometimes many fewer, than the ideal 6
+or 7.)

docs/genindex.rst

+Index
+========

docs/intro.rst

+Introduction
+============
+
+.. include:: ../README.rst
+   :start-line: 2

docs/usage.rst

+Usage
+=====
+
+See ``import csppfetch; help(csppfetch.Downloader.__init__)`` for details on
+the arguments to Downloader.
+
+TODO: Expand on WHY you'd use various options.
+
+
+
+
+``csppfetch.Downloader.download_for_time`` implements the 
+`CSPP Geo ancillary download behavior guidelines <https://docs.google.com/document/d/1phQRbELddAl4AG2EdAvzlJOKdYD0HRu-TpD3fj7J1rA/edit?pli=1>`_.
+It defaults to to abandoning a download after 30 seconds, will retry 3
+failures, and waits 20 seconds between retry attempts. These can be overridden
+with the environment variables ``<prefix>_TIMEOUT``, ``<prefix>_RETRIES``, and
+``<prefix>_RETRY_WAIT``, where ``<prefix>`` is whatever is specified by
+``package_env_id`` in the ``csppfetch.Downloader`` constructor. ``packages_env_id``
+should probably end in "_ANCIL_" to best match the guidelines, so you might use
+``package_env_id="CSPP_GEO_AITF_ANCIL_"`` instead of ``package_env_id="CSPP_GEO_AITF"``. Similarly,
+you can replace the default URL in ``url_base`` with a comma seperated list using
+the ``<prefix>_URL`` environment variable.
+
+By default download_for_time seeks the nearest preceeding time relative to the
+time passed in.
+
+
+
+
+