Using gospew to print out complex data structures when Equals fails

When comparing structs, maps, arrays and slices, this makes the failure message easier to read and actually shows details of the nested data structures.  Here's an example output:

```
Location:       yamlconf_test.go:119
	Error:		Not equal:
			---- Expected ----
			(*yamlconf.TestCfg)(0xc2080387c0)({
			 Version: (int) 1,
			 N: (*yamlconf.Nested)(0xc20800e0c0)({
			  S: (string) (len=1) "3",
			  I: (int) 3
			 })
			})
			
			--------------
			---- Actual ------
			(*yamlconf.TestCfg)(0xc208038e90)({
			 Version: (int) 1,
			 N: (*yamlconf.Nested)(0xc20800e780)({
			  S: (string) "",
			  I: (int) 55
			 })
			})
			
			--------------
	Messages:	Config from updated file should contain correct data
```