Added test for rereading HTML output of VOtable
Restructured reader by making HTMLInputter responsible for finding table data
Removed VOtable test
Moved check for <tr> tags to HTMLInputter, removed old test
Modify HTML multi-col test file to be more stressing
Change multi-col handling to leave vals as strings for TableOutputter
Add a table row with a string but no data elements
Simplify logic for selecting table rows
Fix to set blank data values as missing
Add test of informative error if table id not found (currently failing)
Add sanity-check tests of column name handling
Remove unused imports
Added pytest markings to new HTML tests
Made error message more informative for 'table not found'
Restored check for whether id is supplied in identify_table for tests
Fixed expected behavior in test
Altered test for string representation of error
Fixed problem in test with unicode/ascii difference
Removed unused test file
Deep copying of htmldict, made call in HTMLOutputter more idiomatic