Read text files from disk
refactor text extraction and fix test
Remove progress bar and add logging

We can't supress stderr with backticks, so remove progress bar
and add in some logging so we can raise issues in tika and upstream
for files we cannot extract.
Remove #extract_text from AttachmentData

it's only used in the rake task.

Also made the rake task logging better.
Merge pull request #715 from alphagov/index-attachment-updates

Use the text version of the files on the file system for the indexing