Merge pull request #161 from demarey/master

Add some methods to abstract file system access
Merge pull request #163 from demarey/master

Don't hide events to Pharo during tests...[builds green for non-Pharo-2.0 platforms](https://travis-ci.org/dalehenrich/metacello-work/builds/7359616)
Merge pull request #164 from demarey/master

Updates for Pharo2 support.
Merge pull request #165 from demarey/master

Updates for Pharo2 support.
Merge remote-tracking branch 'christophe/master' into issue_167
refactor handling of Metacello-TestsPharo20MC and Metacello-TestsCommonMC

move Metacello-TestsCommonMC to Metacello-TestsCommonMC.common
move Metacello-TestsPharo20MC to Metacello-TestsCommonMC.pharo20
update BaselineOfMetacello to match
add GemStone-3.1.0.3, Pharo-3.0 and Pharo-2.0 to lineup
platform-specific implementation of MetacelloTestsMCPackage
not sufficient to rename file ... have to rename method selector, too
pare down lineup ... take a stab at Pharo-2.0 test errors