sync max body size

[sjanssen2]

I am not totally sure if my analysis is accurate. Here is my understanding of the problem.

While setting up a qiita instance, we stumbled upon issues when uploaded files. File < chunk size were not affected. Also, this error only occurred when qiita run within the nginx setup, not as pure python instance. It looks like there is a default maximum body size for GET commands of 1M in nginx. Therefore, you might want to increase this size in the nginx_example.conf or at least leave a comment to inform others.
I have not tested to set this value to 3M, but I recognized that the actual size of the payload various around 3400000 byte, thus some buffer could be useful.

Ideally, both values would be sources from a configure file instead of "hard coding" them into the javascript and the nginx config file.

[antgonza]

Thank you @sjanssen2; I think your explanation makes sense.

Now, I'm not sure if having this in a config file would actually be possible, to start the nginx config file is completely independent of qiita (in the main qiita system, they are actually started by different users). Anyway, the change looks good and will merge when the tests passes.

[coveralls]

coverage: 92.894%. remained the same
when pulling fc5991a on sjanssen2:patch-1
into 1c1a4a7 on qiita-spots:dev.