Add warning about lookup type for CharFields/TextFields

I had an issue with it and #django IRC said that it's quite common issue so... here we go!
Fix line-lenght
Fix typo in widgets docs
Merge pull request #129 from chuwy/patch-1

Fix typo in widgets docs
Merge pull request #125 from daGrevis/patch-1

Add warning about lookup type for CharFields/TextFields