Merge pull request #13 from jaumeortola/master

Add frequency data to dictionary (speller)
fix a bug for words with non-encodable characters

this showed in a dictionary with freq info, test case added ("a" is in
the dictionary and has "T" frequency class, so SEQUENCE_IS_A_PREFIX is
found for non-encodable "aõh").
doc the fix
[bug workaround] limit the replacement search
Moved bugfix to 1.8.3
Adding 1.8.3 entries
Add candidates as they are in the dictionary, not mixed-case versions