Fixes for several compiler warnings

My default compiler warnings brought up some fairly trivial issues when I compiled SVPullToRefresh. They were straight forward to fix/suppress so I thought I'd send along a PR. 

Included are fixes for -Wsign-conversion, -Wfloat-equal, -Wconversion and -Wnewline-eof. 

There are no functional changes and I've only updated the main four SVPullToRefresh/Infinite scroll files as I wasn't concerned with the demo project.