Fix buildBody method (#16)
Fix buildBody method (#16)

* Fix float type to str type

If upload_id type is float, uploadVideo will have TypeError.
```python
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-3-d610562e7b00> in <module>()
----> 1 insta.uploadVideo('/home/tu/test.mp4', 'Hello guys')

/home/tu/.virtualenvs/money_tool/local/lib/python2.7/site-packages/InstagramAPI/src/Instagram.pyc in uploadVideo(self, video, caption)
    330         :return: Upload data
    331         """
--> 332         return self.http.uploadVideo(video, caption)
    333 
    334     def direct_share(self, media_id, recipients, text=None):

/home/tu/.virtualenvs/money_tool/local/lib/python2.7/site-packages/InstagramAPI/src/http/HttpInterface.pyc in uploadVideo(self, video, caption)
    226         ]
    227 
--> 228         data = self.buildBody(bodies, boundary)
    229         headers = [
    230             'Connection: close',

/home/tu/.virtualenvs/money_tool/local/lib/python2.7/site-packages/InstagramAPI/src/http/HttpInterface.pyc in buildBody(self, bodies, boundary)
    582                 for header in b['headers']:
    583                     body += ("\r\n" + header)
--> 584             body += ("\r\n\r\n" + b['data'] + "\r\n")
    585         body += ('--' + boundary + '--')
    586 

TypeError: cannot concatenate 'str' and 'float' objects
```

* fix buildBody method

danleyb2/Instagram-API