Change get_reader.from_excel() to accept keyword arguments

[shawnbrown]

Change get_reader.from_excel() to accept keyword arguments that are passed on to the call to xlrd.open_workbook() in get_reader.py).

See...

get_reader/get_reader.py

Line 372 in f481d95

def _from_excel(path, worksheet=0):

get_reader/get_reader.py

Line 383 in f481d95

book = xlrd.open_workbook(path, on_demand=True)

get_reader/get_reader.py

Line 603 in f481d95

def from_excel(self, path, worksheet=0):