BibSort: improved washers

* Improves speed and realiability of BibSort washers by properly
  exploiting textutils.decode_to_unicode() and
  textutils.translate_to_ascii() functions.

* Improves speed of textutils.translate_to_ascii().

* Makes unidecode dependency mandatory.

Signed-off-by: Samuele Kaplun <samuele.kaplun@cern.ch>
1: D400 First line should end with '.', not 'e'
4: I102 copyright year is outdated, expected 2014 but got 2012
28: D209 Put multi-line docstring closing quotes on separate line
28: D203 Expected 1 blank line *before* class docstring, found 0
28: D204 Expected 1 blank line *after* class docstring, found 0
28: D400 First line should end with '.', not 'd'
28: D205 Blank line missing between one-line summary and description
34: D203 Expected 1 blank line *before* class docstring, found 0
34: D400 First line should end with '.', not 's'
37: D102 Docstring missing
45: D401 First line should be imperative: 'Return', not 'Returns'
45: D400 First line should end with '.', not 'e'
49: D401 First line should be imperative: 'Return', not 'Returns'
49: D400 First line should end with '.', not 'e'
53: D400 First line should end with '.', not ':'
53: D205 Blank line missing between one-line summary and description
63:39: E261 at least two spaces before inline comment
63:40: E262 inline comment should start with '# '
68: D400 First line should end with '.', not ':'
68: D205 Blank line missing between one-line summary and description
78:39: E261 at least two spaces before inline comment
78:40: E262 inline comment should start with '# '
83: D400 First line should end with '.', not 'e'
89: D400 First line should end with '.', not 'e'
95: D400 First line should end with '.', not ':'
95: D205 Blank line missing between one-line summary and description
118: D400 First line should end with '.', not ':'
118: D205 Blank line missing between one-line summary and description
129: D401 First line should be imperative: 'Return', not 'Returns'
129: D400 First line should end with '.', not "'"
129: D200 One-line docstring should not occupy 3 lines