Misc number fixes

* Allow strings/json.Number with just zeroes after the decmial point to be converted to integer`
* Allow nil in ToFloat*
* Remove some test duplication
* replace testify with quicktest
* Enable integer and float conversion of time.Weekday values

Fixes #139
Fixes #141

Author: bep

.github/workflows/go.yml

@@ -10,7 +10,7 @@ jobs:
   build:
     strategy:
         matrix:
-          go-version: [1.17.x, 1.18.x]
+          go-version: [1.16.x, 1.17.x, 1.18.x]
           os: [ubuntu-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     steps: