creates FAQ page in docs (#522)

* creates FAQ page

* revise index.md

* tweaks

docs/index.md

@@ -1,20 +1,23 @@
-# cellxgene
+_cellxgene_ is an interactive data explorer for single-cell transcriptomics data designed to handle large datasets (1 million cells or more) and integrate with your favorite analysis tools
 
-cellxgene is an interactive data explorer for single-cell transcriptomics data designed to handle large datasets (1 million cells or more) and integrate with your favorite analysis tools
+## features
+
+- Flexible selection and coloring of cells
+- Differential expression of arbitrary sets of cells
+- Single-gene analyses
 
 ## getting started
 
 install the package
 > `> pip install cellxgene`
 
-preprocess the data for use with cellxgene (optional)
-> `> cellxgene --prepare dataset.h5ad -o processed.h5ad`
-
 launch the web app
 > `> cellxgene --launch processed.h5ad`
 
-## features
+## getting help
 
-### help and contact
+We'd love to hear from you!
 
-Have questions, suggestions, or comments? You can come hang out with us by joining the [CZI Science Slack](https://join-cziscience-slack.herokuapp.com/) and posting in the `#cellxgene-users` channel. As mentioned above, please submit any feature requests or bugs as [Github issues](https://github.com/chanzuckerberg/cellxgene/issues). We'd love to hear from you!
+For questions, suggestions, or accolades, [join the `#cellxgene-users` channel on the CZI Science Slack](https://join-cziscience-slack.herokuapp.com/) and say "hi!".
+
+For any errors, [report bugs on Github](https://github.com/chanzuckerberg/cellxgene/issues).