Rebased Mercurial Support
Fix running the tests without mercurial username
Added documentation about test prerequisites for mercurial
Removed some dead code
Fixes based on code review by @sethvargo
remove uncessary File.join call
Revert "remove uncessary File.join call"

This reverts commit 82c6ae8eeea89115056267725b7c2238ec4e05fe.
remove useless File.join
Code style fixes
Fixes based on code review
Merge pull request #746 from m-ryan/master

Mercurial Support (rebased)