Coverage tests fix

Previous tests forgot to call Exit-CoverageAnalysis, and left a bunch of orphaned breakpoints in the session as a result.
Better output for Hashtable Key-Value pairs in CodeCoverage report

The "Command" text for expressions in a hashtable should now display the entire "Key = <Expression>" text instead of just "<Expression>"
Merge pull request #149 from dlwyatt/CoverageTestFix

Coverage tests fix
Merge pull request #150 from dlwyatt/CoverageHashtableOutput

Better output for Hashtable Key-Value pairs in CodeCoverage report
Add Changelog entries for the two recently merged PRs and references to previously merged PRs
Fix relative paths for OutputXml

The xmlwriter method used to output nUnit report can resolve relatives
paths by itself, but its current directory is not necessarily the same
as what PowerShell sees as the current directory. I have to resolve the
path beforehand working around the limitations of Resolve-Path.
Remove Validate-Xml

Removing validate xml function which was replaced in the tests with less
general way of validating nUnit output xml files.
Remove legacy object adaptations support

This has been long talked about and the new 3.0.0 release is the ideal
release to finally get rid of the legacy way of using pester.
Remove tests testing usage of global scope

Removed the unused code that used to test the usage of global scope.
Looking through the code the only global variable is the global
TestDrive variable. This variable is provided for backwards
compatibility.

$pesterHome = Get-Module Pester | Select -ExpandProperty Path |
Split-Path
Get-ChildItem -Path $pesterHome -Include *.ps1, *.psm1 -Recurse |
Get-Content |
Select-String -Pattern '(\$global)|(-Scope\s+Global)'

Testing this properly needs running pester inside pester tests (not sure
if the whole test suite should be run or just a single test is enough)
and comparing the state of the global scope before and after run. Making
mental note of this and moving it to low priority folder.
Update the readme.md
Coverage output now also includes function name
Merge pull request #152 from dlwyatt/AddFunctionToCoverageOutput

Coverage output now also includes function name
add function name to code coverage output changelog
Got NUnit export working on PowerShell v2 again.

Fixes #153

Assignment to WriteEndDocumentOnClose was unnecessary, since it defaults to True anyway.  The property doesn't exist prior to .NET 4.5, and the code appears to generate identical files either way.

While running the unit tests on PowerShell 2.0, also came across another instance of v2 weirdness (foreach on a null collection executing the body once.)  Added test for null before enumerating.
Merge pull request #154 from dlwyatt/OutputXmlV2Compatibility

Got NUnit export working on PowerShell v2 again.
Do not show warning if resolved code coverage path is folder

When wildcard in code coverage path is used it resolves and reports all
files that are not .ps1 or psm1 files. This included folder paths which
might appear to the user that no script in the path is  included, which
is not true. Warnings for folder paths are no longer shown.
Allowing Pester to analyze its own coverage

Re-added the plumbing that allows Pester to do coverage analysis of its own code with a closer to accurate result.  This is extremely slow, though, so I'll probably just keep this branch separate and rebase it as necessary.