Fixes #103 - Fix assertion, wrap lines, add safety assertion

- Assert errorCount() == 1 before asserting error conditions, avoid
  bad access
- Assert snapToLines == true rather than false when it's expected to
  be the default setting, as per the rules of the spec.
- Use convenience error condition assertion function
- Wrap lines to 80 cols
Fixes #103 - Assert BAD_VALUE rather than UNEXPECTED_WHITESPACE

- There is no bad whitespace at column 30 in the test data, and it
  doesn't really make sense to test against that. Changed this to
  BAD_VALUE
Merge pull request #103 from caitp/issue-103

CueSettingLine.PercentNegative incorrectly ASSERT_FALSE(snapToLines())