Sorted out mime initialization.

Every mime related function in main __init__.py has a flag check for the
check if initialization has already done. This is nonsense, since it
should be done implicitly early on the converter is starting.

This commit straight the things out, and initialization is done in cli
module.

Also, function guess_type was removed, since it's just a proxy for
mimetypes.guess_type function.

ebook_converter/__init__.py

@@ -1,12 +1,10 @@
 import math
 import os
 import pkg_resources
-import random
 import re
 import sys
 import time
-import urllib.parse
-import urllib.request
+import mimetypes
 
 from functools import partial
 
@@ -28,35 +26,17 @@ if False:
     fcntl, win32event, isfrozen, __author__
     winerror, win32api, isbsd, config_dir
 
-_mt_inited = False
 
-
-def _init_mimetypes():
-    global _mt_inited
-    import mimetypes
+def init_mimetypes():
     mimetypes.init([pkg_resources.resource_filename('ebook_converter',
                                                     'data/mime.types')])
-    _mt_inited = True
-
-
-def guess_type(*args, **kwargs):
-    import mimetypes
-    if not _mt_inited:
-        _init_mimetypes()
-    return mimetypes.guess_type(*args, **kwargs)
 
 
 def guess_all_extensions(*args, **kwargs):
-    import mimetypes
-    if not _mt_inited:
-        _init_mimetypes()
     return mimetypes.guess_all_extensions(*args, **kwargs)
 
 
 def guess_extension(*args, **kwargs):
-    import mimetypes
-    if not _mt_inited:
-        _init_mimetypes()
     ext = mimetypes.guess_extension(*args, **kwargs)
     if not ext and args and args[0] == 'application/x-palmreader':
         ext = '.pdb'
@@ -64,9 +44,6 @@ def guess_extension(*args, **kwargs):
 
 
 def get_types_map():
-    import mimetypes
-    if not _mt_inited:
-        _init_mimetypes()
     return mimetypes.types_map