Document uses for map

This adds documentation to `map` on a couple of common uses. One is
using a different implementation of a common API. The other is ignoring
an optional dependency. Closes #283
Fix some documentation format issues

- Fix typo (backtip instead of single quote)
- Use consistent indentation in code examples
- Use consistenly double quotes through code examples
- Use consistent indentation for `script` tags examples
Merge pull request #282 from bitovi/fix-docs-format

Fix some documentation format issues.
Merge pull request #285 from bitovi/map-docs

Document uses for map
Add simple assert function to steal.dev object.

Closes #286.