More ways for blt to lose tweets

The LAST_ACCESS time is updated even if the get request doesn't succeed so tweets are lost if twitter times out etc.

A partial solution would be to store the time in a variable immediately after the request and only log it to the file if the request was deemed to be successful.

A better solution (that wouldn't miss tweets sent during the get time) would be to store the time in a variable immediately before the request. Because there
is then the possibility of duplicate tweets, the last line of output from each request would be stored in the file and then time tweets are retrieved, any line upto and including the previous stored line would not be shown.