Fix: trailing or leading white space for exon coordinates will now be
striped. If the user enters no coordinates, a dialog will now appear.
Removed cwd as default directory for file dialog specifying output
text file. The previous default may have been confusing for users.
Fix: when saving as html, now check to see if output.txt is the same
file when copying (cannot copy a file to itself).
Added better checking and sanitization of user typed bigwig input