Support using < to set up colspan

[kherock]

Hi, thanks for the helpful library. I was wondering if you'd be open to supporting the < character to set up colspan. I find the examples with > hard to read since it doesn't really align with the use of ^ for rowspan as a left-to-right, top-to-bottom reader.

I think the main example in the README is a bit easier to read if the column contents are shown in the left-most cell:

| Head 1       | Head 2       | Head 3       | Head 4       |
| ------------ | ------------ | ------------ | ------------ |
| Merged (2x1) | <            | Cell         | Cell         |
| Merged (1x3) | Merged (2x2) | <            | Cell         |
| ^            | ^            | <            | Cell         |
| ^            | Merged (3x1) | <            | <            |

[Airkro]

Add options.mergeTo in v0.1.2, now < is available when options.mergeTo === left, please send me feedback.