conflict with SDK GoogleAnalytics

constant name **kDefaultTimeout** change to **kDefaultRequestTimeout** because there is conflict with SDK GoogleAnalytics
Merge pull request #24 from jerson/patch-1

conflict with SDK GoogleAnalytics
expectedDataLength may be -1, then uint64_t will make "Not enough free disk space" error occur.
Merge commit '8cf2d2b4146ff728e07d3a0da9bf51519a85318b'