Expand documentation, add discussion on counterintuitive behavior

[jlchan]

• reorganized the README sections
• added some minor extra clarifications on getindex creating struct entries on the fly
• added a section on counterintuitive behaviors (see setindex! and setfield! of immutable types #181 (comment) and Indexed ".=" behavior and Base.dotview #187). Addresses Indexed ".=" behavior and Base.dotview #187
• added example section and a StaticArrays example

[jlchan]

Ah, this probably shouldn't be merged until after #186 because the examples include StaticArrays.

[jlchan]

Other possible things that might be useful to document? I don't know if it'd be necessary to add docs for

• LazyRow efficiency and @inbounds? Should indexing return a LazyRow by default? #112
• convert and setindex! Document setindex! / push! calling convert JuliaLang/julia#40498
  I haven't looked too closely at those, however.

[ranocha]

This seems to be a nice addition from my point of view

[piever]

Thanks again for the PR and sorry I haven't come back to it in a while, this is a massive improvement to the current docs!

I've left a few minor comments, but it's mostly very good.

About the commented things in the make.jl file, could you remove them and open a "documentation TODOs" meta issue instead? These PR is quite big already, so I thought those could be handled in a future separate PR.

[jlchan]

Thanks again for the PR and sorry I haven't come back to it in a while, this is a massive improvement to the current docs!

No worries at all, glad you found it useful :)

About the commented things in the make.jl file, could you remove them and open a "documentation TODOs" meta issue instead? These PR is quite big already, so I thought those could be handled in a future separate PR.

Done in #201