closes#2008
Changes:
- Drop `asObservable()` since it is deprecated in RxJS 5 (see the
[migration
guide](https://github.com/ReactiveX/RxJS/blob/master/MIGRATION.md#operat
ors-renamed-or-removed)).
- Drop `+` from hero search query URL: `app/heroes/?name=${term}+`. At
best it is interpreted as a regex op that serves no purpose, at worst,
it gets interpreted as a space (cf. [HTML 4.01 section
17.13.4](https://www.w3.org/TR/REC-html40/interact/forms.html#h-17.13.4)
).
- Rename `searchSubject` to `searchTerms`
- Other minor tweaks to prose.
This work is in preparation for #1924.
Note: toh-6 tests pass.
04d5337b75