Adds float32, uint, uint64, uint32, uint16, and uint8 throughout.

Fixes #33

Test coverage goes from 75.6% to 100%

In commit d1139ba, I removed a date format for "RFC3339 without T" that
I misidentified as a reduntant format.  This commit adds it back with a
test.

Add missing time formats, remove duplicate formats, and test all
supported formats.

```
BenchmarkTooBool-4   	  500000	      2781 ns/op	      49 B/op	       3 allocs/op
```

Fixes #1

It used to return zero valeus in some cases. The details are described
in [this issue](https://github.com/spf13/viper/issues/203). More cases
were also added in the unit test `TestToDuration()`

* Update caste.go

bug fix

json config, for example:
{ "test" : ["abc", "123"] }

* update test

Resolves #18

Fixes #13

Now it accepts any slice or array type that contains a type supported by ToIntE.

[close #12]

ToStringMapBool is useful for a map of flags in a configuration file.