Minor release with updates to reflect Socrata API changes

• Change Remove limit of 50,000 in the SoqlQuery::limit(); older datasets will simply throw an exception with an error message stating the limit.
• Change API 2.0 and 2.1 datasets can now be differentiated with SodaDataset::getApiVersion()
  • This change also changes the return type of this function from int to double. Unless you explicitly used is_int in your code, this won't break any code.