Fixed panic when callerName doesn't have package

The callerName can be in two formats:

    com/remogatto/prettytest.(*testSuite).Should_be_cool
    (*testSuite).Should_be_cool

Currently only the first case was handled and the second caused a panic.
This commit allows support for both.
Simplified BDDFormatter's splitString a bit
Merge pull request #14 from pranavraja/master

Fixed panic when suiteInfo.callerName does not contain the package
Add gocheck compatibility
Add Not assertion
Add Error
Better output
Heavy refactoring
Run gofmt
Add assertions.go
Small refactoring
Update README
Improve documentation
Merge branch 'master' of https://github.com/remogatto/prettytest

Conflicts:
	prettytest.go
implemented type checking so that suite.Not can't be used on non-Assertions
implemented suite.False again because I missed it when it went away :)
Merge pull request #16 from mzimmerman/master

Forcing suite.Not() to be on an Assertion instead of a bool so that it can't be misused