Add documentation for ipfx

I took a look through the docs.

landing:

[x] landing page says ipfx is python 2/3. We only support 3 now
[x] (nice to have) bolded class names in text should be links to apidocs
[x] the "analyze a data set" section should use the new dataset constructor
[x] the "analysis pipeline" section should be fleshed out and its value for external users described
[x] Describe package's function in more detail at the beginning. It should answer the question of "How this package could be useful to me?" rather than describing what we did here at Allen. Which features can package compute and for which stimuli? Link to list of features.
[x] Instead of saying "software is designed for use in the Allen Institute for Brain Science electrophysiology data processing pipeline" list how it could be used at different scales of processing. From single t v i sweeps to building a processing pipeline
[x] In Stimulus Specific Analysis introduce Sweep before Sweep_Set
[x] add QC example. QC is mentioned but no example is given
[x] In Analysis Pipeline introduce the notion of a pipeline as a next step in the scaling of the ipfx usage. Remove references to particular scripts (e.g, sweep_extraction). They are described in detail on a Pipeline page.
[x] Questions section on the left-hand side is AllenSDK specific. Is that a part of the template that cannot be changed?
[x] Liming the landing page to description of what the package is doing. Move all quick examples (the how) to the separate QuickStart page. Add to the QuickStart Page the example of running the DataSet rather than having it in a separate page.
[x] Restructure the "Dataset and Stimuli" page to make it largely about stimuli describing different stimuli types (ideally with plots) and the intricacies of the stimulus_ontology
[ ] Add new page describing how to download data. Any way to access data from dandi based on specimen_id??

Api Documentation

[x] Docstrings do not build correctly "Unexpected section title."

installation:

[x] once ipfx is on pypi, update installation page to suggest pypi install
[x] mention that git-lfs is needed to get our test data

credits:

[x] add contributors

data sets and stimuli:

[x] fix weird bolding and broken links
[x] intro can be tightened up a bit
[x] use new dataset constructor
[x] when mentioning NWB in text, should expand the initialism and link to https://www.nwb.org/ (at least the first time on a page). People might not know what an NWB file is.

gallery of examples: Some of these could use:

[ ] more textual description
[ ] more explicit variable names
[ ] change code examples to create dataset from downloaded nwb file. Do not use AllenSDK api
[ ] unify template to have figure with output to show after the code snippet
[ ] in All Analysis remove test sweeps with filtered_sweep_table rather than hacking it around

qc and analysis pipeline:

[x] this whole page is missing. I think it is supposed to be the "how do I replicate the AIBS pipeline" guide. We could also use it to give examples of how to setup inputs for and run the argschema modules.

api documentation:

[x] Our docstrings seem to be rendering. :fire:

history:

[x] Another stub. We decided to use the Github releases, right? Let's just replace this page with a link

README.md:

[x] we can remove the deprecation warning
[x] add a link to the docs and examples
[x] add links to new contrib guidelines

AllenInstitute / ipfx

Add documentation for ipfx #36