Add try seq[0] to first
Add try seq[0] to first

This makes getting elements from tuples and lists much faster
but significantly slows down getting elements from iterators

I believe that first(indexable) occurs more frequently in common
operations.

bartvm/toolz,quantopian/toolz,berrytj/toolz,jcrist/toolz,pombredanne/toolz,karansag/toolz,cpcloud/toolz,obmarg/toolz,cpcloud/toolz,jdmcbr/toolz,obmarg/toolz,whilo/toolz,berrytj/toolz,jdmcbr/toolz,llllllllll/toolz,jcrist/toolz,bartvm/toolz,machinelearningdeveloper/toolz,karansag/toolz,pombredanne/toolz,whilo/toolz,simudream/toolz,quantopian/toolz,llllllllll/toolz,simudream/toolz,machinelearningdeveloper/toolz