Add error message for invalid test suit

[IharYudziankou]

When expected response had been put into body section as json(see example below), runtime error happens.
Stack trace should be replaced with Error message with explanation of the reason of fail.

Piece of test suit json:

...
          "body": {
            "arr": [
              {
                "fld": "val"
              }
            ]
          }
...

Console output:

C:\ . . . \bozr.exe -i -H http://localhost/rest C:\ . . . \bug.suite.json
panic: runtime error: comparing uncomparable type map[string]interface {}

goroutine 19 [running]:
main.findDeep(0xc0421fc500, 0x1, 0x1, 0x781c20, 0xc0421a8570, 0x8000102)
	/Users/xander/Development/Sandbox/gotest/src/github.com/kajf/bozr/matchers.go:142 +0xae
main.findDeep(0xc0422b3ea0, 0x1, 0x1, 0x781c20, 0xc0421a8570, 0x1)
	/Users/xander/Development/Sandbox/gotest/src/github.com/kajf/bozr/matchers.go:137 +0x10d
main.SearchByPath(0x781c20, 0xc0421f4210, 0x75ec60, 0xc0420023c0, 0xc042008880, 0xc, 0xf09928, 0xc0422b1690, 0x410911)
	/Users/xander/Development/Sandbox/gotest/src/github.com/kajf/bozr/matchers.go:67 +0x17b
main.checkExpectedPath(0x781c20, 0xc0421f4210, 0x79ad80, 0xc0422c26e0, 0x0, 0x4d71c2)
	/Users/xander/Development/Sandbox/gotest/src/github.com/kajf/bozr/expect.go:131 +0xc5
main.responseBodyPathCheck(0xc0421f4150, 0x79ad80, 0xc0422c26e0, 0x7fe050, 0xc0421d4000, 0xc0422b1758)
	/Users/xander/Development/Sandbox/gotest/src/github.com/kajf/bozr/expect.go:233 +0x15f
main.BodyExpectation.check(0xc0421a8540, 0xc0421f4150, 0xc0421be320, 0x95)
	/Users/xander/Development/Sandbox/gotest/src/github.com/kajf/bozr/expect.go:109 +0x11e
main.call(0xc04200887c, 0x2, 0xc0421a8270, 0xc042008208, 0x3, 0xc04200c200, 0x37, 0xc0421a83c0, 0x0, 0x0, ...)
	/Users/xander/Development/Sandbox/gotest/src/github.com/kajf/bozr/main.go:276 +0x8a2
main.runSuite(0xc042080057, 0xe, 0xc04200887c, 0x2, 0xc0421a88d0, 0x1, 0x1, 0x0, 0x0, 0x0)
	/Users/xander/Development/Sandbox/gotest/src/github.com/kajf/bozr/main.go:181 +0x55d
main.runSuites(0xc04203e300, 0xc04203e360, 0xc042055910, 0x7fe068)
	/Users/xander/Development/Sandbox/gotest/src/github.com/kajf/bozr/parallel.go:45 +0xf7
created by main.RunParallel
	/Users/xander/Development/Sandbox/gotest/src/github.com/kajf/bozr/parallel.go:19 +0xc7

Process finished with exit code 2