Fix reading error for job sizes around 490 bytes

When the beanstalkd status is read into the initial buffer, the expected size
doesn't take \r\n after job data into account.
For jobs where status_size + job_data = 511 the \n will be left in the socket's
buffer. This breaks the next command because the \n is not expected when the
next beanstalk status is read.
Merge pull request #9 from swehner/fix-read-initial-buffer

Fix reading error for job sizes around 490 bytes