adding BeNullOrEmpty assertion. This fixes #39
Adding Throw assertion which fixes #37

This required reording AssertionMethod arguments. For methods that
only need pipeline argument it's needed to move value to the first
arg.
updated CHANGELOG and Examples with new functionality and fixes
Changing assertion functions to follow naming convention

Apologies for the large commit. In this commit

- all assertion functions follow the form Pester<function>
- removed redundant tests
- 1 single test to test for all failure messages
adding Exist assertion function
moving as many pester tests to new assertions
adding Should Match and updating Pester tests
all Pester tests use new assertions
enabled workaround that fixes #19 and fixes #27

Pester itself is using the new assertion format. So if you only
use those you can disable the old style assertions which have been
causing these issues.

The flag is -DisableOldStyleAssertions

For backwards compatibility these will be enabled by default.

For release 2 of Pester, these will be disabled by default and you
will have to explicitly enable them.
adding new functionality to CHANGELOG
assertion tests no longer have cyclic dependencies
adding Contain assertion which will fix #13

future versions of Contain should test against collections
and perhaps hashes. At least now there's a test fixture to
add that aditional functionality
getting ready for 1.2.0 release
releasing 2.0.0. Disabling old style assertions by default
making switch conform to naming standard
The $failedTestsCount was null

$Global:TestResults.FailedTestsCount was null.

I was trying to figure out why the ($p = Start-Process -FilePath
Powershell -ArgumentList "invoke-pester -enableExit") returned process,
wasn't reporting an error code above zero ($p.ExitCode == 0) when there
were pester errors.  I tracked it down to this line.
Merge pull request #44 from mitchelldavis/master

Exit-WithCode Error
updating CHANGELOG for new fix and prepping for release
closed #40 lookig for line number in test file and eliminating line in should.ps1
test failures were not failing build