Troubleshooting guide

[Nick Burch]

Hi All

I've had a go at writing up a troubleshooting guide on the wiki, hopefully 
covering the main problems people face (content detected wrong, parser 
missing etc). It's linked from the front page and at
https://wiki.apache.org/tika/Troubleshooting%20Tika
Please expand and correct it as needed!

Thanks
Nick