Added a waterML2 function and rename column function. The rename columns function will check the parameter code and use SRS name to name columns.

Updated R requirement to > 3.0 since having a knitr vignette is not compatible with earlier versions of R.

Added some easy checks to the water quality data to assure that the number of samples returned matched what the water quality portal said should return.

Added new function 'getDataAvailability' to find what parameters, stats, and period of record for an individual site.