Nested fetch state

[dmitryshelomanov]

Problem

Many fetch state in a flat state object

Solution

Add support fetch in nested state
For example

  const initial = {
    fetching: {
      main: initialFetching,
      apply: initialFetching,
    },
  }
  const symbiotes = {
    fetchNewsHandler: createFetching("fetching.main"),
    applyNewsHandler: createFetching("fetching.apply"),
  }

[coveralls]

Pull Request Test Coverage Report for Build 32

• 7 of 7 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+2.2%) to 47.273%

---

Totals
Change from base Build 31:	2.2%
Covered Lines:	23
Relevant Lines:	43

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 35

• 7 of 7 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+2.2%) to 47.273%

---

Totals
Change from base Build 31:	2.2%
Covered Lines:	23
Relevant Lines:	43

---

💛 - Coveralls

[sergeysova]

Please, add tests to check for deep level foo.bar.baz

[dmitryshelomanov]

@sergeysova I added random deep lvl