Added check for valid user-provided URL
Cleaned description of readUrl() function
Implemented return() in readUrl() function
Simplified check for URL scheme
Improved validation of 4x4 -- added isFourByFour()
Switched to build_url() to build valid URL
Added unit test for checking valid 4x4
Added unit test to check for valid URL
j/k, now read.socrata() works with human-readable URLs
Commented-out SocrataNotResource test, added human-readable test
Fixed type-o in checking for valid 4x4