The refresh param now takes seconds rather than ms

Updated the default value of the refresh param, which is now specified in seconds rather than milliseconds.

Please see [this commit](https://github.com/sensu/uchiwa/commit/71880ca3ed415af3c03d618620830d13e4c6f99e#diff-04c6e90faac2675aa89e2176d2eec7d8R65)