use fgets instead of fread in Stomp::readFrame()

fread reads up to specified number of bytes or EOF.
fgets reads up to "\n", number of bytes or EOF.

The problem with fread is that if there is more than one Frame
on the socket, it will read the current Frame and part of the next
Frame.  Stomp::readFrame() is expected to just read the next Frame.
Merge pull request #22 from boonedox/master

bug fix for Stomp::readFrame, was occasionally reading more than one Frame, this merge prevents this as it only reads up to \n and checks for end of frame before anything of the next frame is read