Add more general file utils to the cache module and rename it 'store'

EDdA/classification/nGramsFrequencies.py

-from EDdA.cache import Cache
+from EDdA.store import Cache
 from EDdA import data
 import nltk
 import pandas

EDdA/cache.py → EDdA/store.py

-import json
 import os
 import os.path
 
+def preparePath(template, **kwargs):
+    path = template.format(**kwargs)
+    os.makedirs(os.path.dirname(path), exist_ok=True)
+    return path
+
 class Cache:
     ROOT = "cache"
 
-    def filePath(symbolicPath):
-        return "{root}/{path}".format(root=Cache.ROOT, path=symbolicPath)
-
     def __init__(self, loader, pathPolicy=lambda *args:str(args)
             , serializer=None, unserializer=None):
         self.RAM = {}
@@ -26,14 +27,14 @@ class Cache:
 
     def heat(self, symbolicPath):
         if self.unserializer and symbolicPath not in self.RAM:
-            path = Cache.filePath(symbolicPath)
+            path = "{root}/{path}".format(root=Cache.ROOT, path=symbolicPath)
             if os.path.isfile(path):
                 with open(path, 'r') as f:
                     self.RAM[symbolicPath] = self.unserializer(f)
 
     def save(self, symbolicPath):
         if self.serializer and symbolicPath in self.RAM:
-            path = Cache.filePath(symbolicPath)
+            path = preparePath("{root}/{path}", root=Cache.ROOT, path=symbolicPath)
             os.makedirs(os.path.dirname(path), exist_ok=True)
             with open(path, 'w') as f:
                 self.serializer(self.RAM[symbolicPath], f)