Log Message:
Update ruby-simplecov to 0.6.4.

v0.6.4, 2012-05-10 \ 
([changes](https://github.com/colszowka/simplecov/compare/v0.6.3...v0.6.4))
-------------------

  * [BUGFIX] Encoding issues with ISO-8859-encoded source files fixed.
    See https://github.com/colszowka/simplecov/pull/117. (thanks to @Deradon)
  * [BUGFIX] Ensure ZeroDivisionErrors won't occur when calculating the coverage \ 
result, which previously
    could happen in certain cases. See \ 
https://github.com/colszowka/simplecov/pull/128. (thanks to @japgolly)
  * [REFACTORING] Changed a couple instance variable lookups so SimpleCov does \ 
not cause a lot of warnings when
    running ruby at a higher warning level. See \ 
https://github.com/colszowka/simplecov/issues/106 and
    https://github.com/colszowka/simplecov/pull/119. (thanks to @mvz and @gioele)

v0.6.3, 2012-05-10 \ 
([changes](https://github.com/colszowka/simplecov/compare/v0.6.2...v0.6.3))
-------------------

  * [BUGFIX] Modified the API-changes for newer multi_json versions introduced \ 
with #122 and v0.6.2 so
    they are backwards-compatible with older multi_json gems in order to avoid \ 
simplecov polluting
    the multi_json minimum version requirement for entire applications.
    See https://github.com/colszowka/simplecov/issues/132
  * Added appraisal gem to the test setup in order to run the test suite against \ 
both 1.0 and 1.3
    multi_json gems and ensure the above actually works :)