History-version-file creation/updation modified

1) INSTALLATIONS file renamed to install.txt

2) Regarding history-version file: For time being, while creating/updating a particular document, the developer needs to explicitly write code to create/update the history-version file respectively. That is:

    (a) While saving a document, i.e. after document.save() function immediately write:

         history_manager = HistoryManager()
         rcs_obj = RCS()

         # Saving the current document's instance into database
         doc_page.save()

         ''' -- Storing history of this current document's instance -- '''
         if history_manager.create_or_replace_json_file(doc_page):
            fp = history_manager.get_file_path(doc_page)
            rcs_obj.checkin(fp, 1, "Message-you-want-to-give").", "-i")

    (b) While updating a document, i.e. after document.save() function immediately write:

         history_manager = HistoryManager()
         rcs_obj = RCS()

         # Updating instance with modified data
         collection_obj.update({'_id': obj_id}, {'$set': {'content_org': content_org, 'content': content}}, upsert=False)

         # Must fetch from database again, otherwise you won't get the updated data
         node = col_GSystem.GSystem.one({'_id': obj_id})

         # Storing histroy in rcs-version-file
         fp = history_manager.get_file_path(node)
         rcs_obj.checkout(fp)

         if history_manager.create_or_replace_json_file(node):
             rcs_obj.checkin(fp, 1, "Message-you-want-to-give")