Update .gitignore.
Remove accept attribute from file input tag.

Restricting acceptable files to .msa files seems to be more
confusing than helping.

This closes #1.
Remove sorting of rows for display purposes.

Keep the order as defined in the file. The original order is
used anyway when saving.

This closes #2.
Fix DOM generation of the table.

Always generate a text node below a <td> tag. This is later expected
when modifying the DOM after changes.

This closes #3.