Tablesorter Testing (WIP)

### This is a work-in-progress. It does not yet comprehensively test all sorting methods. The following are on the to do list:

- Core tests:
  - Test each option, event & callback
  - Sorting empty cells.
  - Sorting strings in numeric columns.
  - Internal rendering, caching & indexing utilities.
  - Update methods.
- All widgets.
- Pager plugin.
- Include natural sort unit tests?

test-head | num
--- | ---
test-foot | txt
test2 | x2
test1 | x3
test3 | x1
Info
testB | x5
testC | x4
testA | x6

1 | 2 | 3 | 4
--- | --- | --- | ---
a | b | c | d
z | y | x | w

1 | 2 | 3 | 4
--- | --- | --- | ---
A43 | -35 | 01 | -.1
A255 | 33 | 02 | N/A #1
A33 | 2 | 03 | N/A #2
A1 | -5 | 04 | -8.4
A102 | NR | 05 | -2.2
A10 | -1 | 06 | 97.4
A02 | 1 | 07 | 23.6
A55 | 44 |  | 11.4
A87 | 04 | NR | 5.2
|  | NR |