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4: I102 copyright year is outdated, expected 2014 but got 2012
30:1: E302 expected 2 blank lines, found 1
30: D209 Put multi-line docstring closing quotes on separate line
30: D203 Expected 1 blank line *before* class docstring, found 0
30: D204 Expected 1 blank line *after* class docstring, found 0
30: D400 First line should end with '.', not 'd'
30: D205 Blank line missing between one-line summary and description
36: D203 Expected 1 blank line *before* class docstring, found 0
36: D400 First line should end with '.', not 's'
39: D102 Docstring missing
47: D401 First line should be imperative: 'Return', not 'Returns'
47: D400 First line should end with '.', not 'e'
51: D401 First line should be imperative: 'Return', not 'Returns'
51: D400 First line should end with '.', not 'e'
55: D400 First line should end with '.', not ':'
55: D205 Blank line missing between one-line summary and description
65:39: E261 at least two spaces before inline comment
65:40: E262 inline comment should start with '# '
70: D400 First line should end with '.', not ':'
70: D205 Blank line missing between one-line summary and description
80:39: E261 at least two spaces before inline comment
80:40: E262 inline comment should start with '# '
85: D400 First line should end with '.', not 'e'
91: D400 First line should end with '.', not 'e'
97: D400 First line should end with '.', not 'e'
103: D400 First line should end with '.', not ':'
103: D205 Blank line missing between one-line summary and description
126: D400 First line should end with '.', not ':'
126: D205 Blank line missing between one-line summary and description
137: D401 First line should be imperative: 'Return', not 'Returns'
137: D400 First line should end with '.', not "'"
137: D200 One-line docstring should not occupy 3 lines