Add file and line numbers to the generated spec methods

[Blacksmoke16]

Add filename and line numbers to generated spec methods:

Before:

F*..F...F.......

Pending:
  ExampleSpec subtract

Failures:

  1) ExampleSpec add
     Failure/Error: @target.add(1, 2).should eq 4

       Expected: 4
            got: 3

     # spec/athena-spec_spec.cr:24

  2) DataProviderTest squares two
     Failure/Error: (value ** 2).should eq expected

       Expected: 5
            got: 4

     # spec/athena-spec_spec.cr:55

  3) DataProviderTest cubes 0
     Failure/Error: (value ** 3).should eq expected

       Expected: 9
            got: 8

     # spec/athena-spec_spec.cr:75

Finished in 334.79 milliseconds
16 examples, 3 failures, 0 errors, 1 pending

Failed examples:

crystal spec src/test_case.cr:256 # ExampleSpec add
crystal spec src/test_case.cr:256 # DataProviderTest squares two
crystal spec src/test_case.cr:256 # DataProviderTest cubes 0

After:

F*..F...F.......

Pending:
  ExampleSpec subtract

Failures:

  1) ExampleSpec add
     Failure/Error: @target.add(1, 2).should eq 4

       Expected: 4
            got: 3

     # spec/athena-spec_spec.cr:24

  2) DataProviderTest squares two
     Failure/Error: (value ** 2).should eq expected

       Expected: 5
            got: 4

     # spec/athena-spec_spec.cr:55

  3) DataProviderTest cubes 0
     Failure/Error: (value ** 3).should eq expected

       Expected: 9
            got: 8

     # spec/athena-spec_spec.cr:75

Finished in 329.93 milliseconds
16 examples, 3 failures, 0 errors, 1 pending

Failed examples:

crystal spec spec/athena-spec_spec.cr:23 # ExampleSpec add
crystal spec spec/athena-spec_spec.cr:54 # DataProviderTest squares two
crystal spec spec/athena-spec_spec.cr:74 # DataProviderTest cubes 0

The failure locations now correctly report the related test method.