Add a error of EntityTooLarge

This fix makes to return 'EntityTooLarge' response,
when the object which user try to upload exceeds the maximum
allowed object size of swift.

Signed-off-by: Kota Tsuyuzaki <tsuyuzaki.kota@lab.ntt.co.jp>
Merge pull request #55 from bloodeagle40234/add_entity_too_large_error

Add a error of EntityTooLarge