Fix #183

The 'check_if_building' function did not return a boolean value if
a tag file was being built. This is incorrect. Additionally the
error message displayed when this case occured was not prominent.
Resolve both of these issues.

- Return False from 'check_if_building' if file is building
- Use 'error_message' rather than 'status_message' for more
  prominent dialog message
- Formatting of file to keep all lines under 80 characters
Merge branch 'bug/183' into development