.gitignore stuff in src/speller directory.
Allow "thru" as it is different enough in spelling from "through".

This adds one word from Xah Lee blog post (issue #52).
Add words from multiple sources.

  A few from the list of words Marco added to his list.

  Some from Xah Lee blog post, closes #52

  Lars Vogel suggestions, closes #62

  A few of my own.