Add table id option to pandas.DataFrame.to_html 
I'm using the pandas.DataFrame.to_html() method to generate a table to embed into a a templated document which references the table via an id. It would be useful if pandas.DataFrame.to_html()  supported a `table_id` parameter:

`df.to_html(table_id='myTable')`

to produce:

`<table border="1" class="dataframe" id='mytable'>`
