#9 - updated mini magick processor to convert to tiff without using comp...

Similar to the RMagick processor, if you attempt to get the OCR text on a jpg using the MiniMagick processor, you'll get an error about compression not being supported.  Here's an example of the error:

```
MiniMagick::Error:
       Command ("mogrify -format tif /var/folders/_j/xc0nx7fd04l_y3bv8yxg108r0000gn/T/mini_magick20140108-6593-16tc0n7.jpg[0]") failed: {:status_code=>1, :output=>"mogrify: CompressionNotSupported `JPEG' @ error/tiff.c/WriteTIFFImage/2589.\n"}
```

This change disables compression for all formats when converting to tif.