Parse .tt2 files as HTML

.tt2 is the extension commonly used for Template Toolkit v2 files. While you can generate any type of file based off TT2 template files, the most common use appears to be generating HTML files and as such, I think it makes sense to parse them as HTML.

I used my project as a test case: https://www.ohloh.net/p/perl-audit-dbi

Here's the output of ohcount before the change:

```
                          Ohloh Line Count Summary

Language          Files       Code    Comment  Comment %      Blank      Total
----------------  -----  ---------  ---------  ---------  ---------  ---------
javascript            5       1894        391      17.1%        107       2392
perl                 22       1400        575      29.1%        643       2618
css                   4        360          4       1.1%          7        371
----------------  -----  ---------  ---------  ---------  ---------  ---------
Total                31       3654        970      21.0%        757       5381
```

And here's the output of ohcount after the change in the attached commit:

```
                          Ohloh Line Count Summary

Language          Files       Code    Comment  Comment %      Blank      Total
----------------  -----  ---------  ---------  ---------  ---------  ---------
javascript            5       1894        391      17.1%        107       2392
perl                 22       1400        575      29.1%        643       2618
css                   6        363          4       1.1%          7        374
html                  3        234          7       2.9%         21        262
----------------  -----  ---------  ---------  ---------  ---------  ---------
Total                36       3891        977      20.1%        778       5646
```