collect_files的文件收集模块出错，会累积之前的项目文件

[liusn]

System and Python Environment

Item	Tooltip	Value
System	uname -a
Python	python -V
Cobra	python cobra.py

Description

在/cobra/pickup.py文件的165行左右，如下

class Directory(object):
    def __init__(self, absolute_path):
        self.absolute_path = absolute_path

    file_sum = 0
    type_nums = {}
    result = {}
    file = []

其中

    file_sum = 0
    type_nums = {}
    result = {}
    file = []

这几个变量声明成全局变量导致多个项目的文件信息都加在了一起，文件数也越来越多，导致后面的识别语言和框架也出错。
修复建议，将上面几个变量放在初始化函数中，如下：

class Directory(object):
    def __init__(self, absolute_path):
        self.absolute_path = absolute_path
        self.file_sum = 0
        self.type_nums = {}
        self.result = {}
        self.file = []

Steps to Reproduce

1. [First Step]
2. [Second Step]
3. [and so on...]

Expected behavior: [What you expected to happen]

Actual behavior: [What actually happened]