Support for postfix conditionals and partial line executions

[gioele]

Code with postfix conditionals like

cond = false
a = 1 if cond
a ||= 2

will show up as 100% covered while it has been covered only partially (I'd say 75%). This is probably because the if cond part has been executed and that makes simplecov think that all the code on that line has been excuted.

[colszowka]

SimpleCov relies on the Ruby STDLIB Coverage library, which is a C0 coverage utility. Check this blog post for a ruby-based explanation of the differences: http://dev-logger.blogspot.com/2008/06/c0-c1-and-c2-coverage.html