Moves khmer exception classes to their own file and defines new base class for all
exceptions.
All exceptions defined in khmer are derived class from khmer::khmer_exception,
including khmer::khmer_file_exception.
fixed issue #86
Move all exception classes definitions in khmer.hh to khmer_exception.hh.
Change all throw std::exceptions to throw khmer::khmer_exception, so all
exceptions thrown by khmer functions are an instance (or derived from) the
latter.
add a test for issue #86 in tests/test_read_parsers.py
Add description of changes to merge branch fix/508.
Fix bad formatting in the Changelog.
modified an error in _khmermodule.cc
fixed line wrap-around
updates based on mr-c's comments
change the coding style
fixed an error in test
Update ChangeLog
Move all include's at the beginning of the file.
Merge pull request #565 from majoras-masque/fix/558

fixed line wrap-around
Merge branch 'fix/508' of github.com:iglpdc/khmer into iglpdc-fix/508
fix ChangeLog formatting
Merge branch 'iglpdc-fix/508'
update based on titus' comments\n1.add 'assert 0, "should fail" at the end of 'try' block\n2. removed the commented-out code