Fixes in the rspec (two fix)

The first commit was also in #87 (sorry)

The 2nd commit "Work around for the slowly-updating test":  Fixes an issue where the test file was being truncated.  

File truncated, seeking to beginning: /var/folders/xm/4mnw8l_n10j3cc3trf484ym40000gn/T/lumberjack-test-file20130916-42600-15laykt

adding @file.size as a work around.