Add snap_x_tolerance and snap_y_tolerance

[dustindall]

Hi @jsvine ,

I was working with a table where i needed to additional snap_tolerance flexibility on the y-axis relative to the x-axis. Therefore, I added a snap_x_tolerance and snap_y_tolerance parameters in the same fashion as text_tolerance and intersection_tolerance.

Thank you for working on this. It is a great package.

Dustin

[jsvine]

Hi Dustin, and thanks for this contribution! I think it's definitely a worthwhile addition.

One request: Could you submit the PR against https://github.com/jsvine/pdfplumber/tree/v0.6.0 instead of master? (I apologize for the lack of clarity about that in the README.md; I'll add a note shortly.)

And one note: Don't worry about the Travis CI test failure; I'm still having trouble getting Travis to play nice with ImageMagick/Wand. I've now temporarily turned off Travis CI until I can sort that out.

Thanks again!
Jeremy

[dustindall]

Yup, made the switch. Do you have an expected release date for v0.6.0?

[jsvine]

Thanks again, Dustin! Merged here: 68f1e1f + 80cdd86

Also added you to the list of thanks: 7a9cfa6

I'd love to be able to provide an expected release date for v0.6.0, but wouldn't want to mislead you!