Update docs

[jeremyliweishih]

Working on docs with notes here.
https://evalml.featurelabs.com/en/update-docs/

• Add flavor to index
• Add skeleton for new content
• New content
  • Optimization
  • Pipelines and Components
  • Guardrails
  • Lead Scoring
• Missing API
  • Components
• Add FAQ

---

• Revise new content
• Revise old content
  • Edit old tutorials and maybe remove some
  • Show inherited methods
  • Decide what needs to be hidden
  • Check docstrings
  • Clean and standardize docstrings
• Remove output from cells when done

---

Further work (further issues):

• Document objective and standard metrics with what they actually entail
• Add more docstring for component and pipeline __init__ (or any other __init__ for that matter)
• doc tests on all relevant methods
• explain Bayesian optimization and other tuners
• API for custom tuners?

[codecov]

Codecov Report

Merging #222 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #222   +/-   ##
=======================================
  Coverage   97.08%   97.08%           
=======================================
  Files          95       95           
  Lines        2742     2742           
=======================================
  Hits         2662     2662           
  Misses         80       80

Impacted Files	Coverage Δ
evalml/demos/fraud.py	100% <ø> (ø)	⬆️
evalml/objectives/fraud_cost.py	100% <ø> (ø)	⬆️
evalml/pipelines/utils.py	100% <ø> (ø)	⬆️
evalml/tuners/skopt_tuner.py	100% <ø> (ø)	⬆️
evalml/pipelines/pipeline_plots.py	91.66% <ø> (ø)	⬆️
...l/pipelines/components/transformers/transformer.py	100% <ø> (ø)	⬆️
evalml/demos/diabetes.py	100% <ø> (ø)	⬆️
evalml/pipelines/pipeline_base.py	97.33% <ø> (ø)	⬆️
evalml/guardrails/utils.py	96% <ø> (ø)	⬆️
evalml/preprocessing/utils.py	83.72% <ø> (ø)	⬆️
... and 10 more

---

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[kmax12]

i think we should remove the optimization section for now. at least until we have more content for it. no need to let that block is merging this in.

[angela97lin]

Yay, lots of good content here! Mostly just added comments regarding grammar + small inconsistencies.

[kmax12]

LGTM. is the plan to create new issues for the few things uncheck and mentioned in the issues description?

[jeremyliweishih]

@kmax12 yep! Everything under further issues.