Extracted many extension classes from FakeExtensions. For #206.
add issue priorities to contribution guidelines
Merge pull request #222 from adamralph/issue-priorities

add issue priorities to contribution guidelines
Merge pull request #221 from blairconrad/206-split-fakeextensions.cs

Extracted many extension classes from FakeExtensions. For #206.
#218 switch from SL4 to SL5
Merge pull request #223 from adamralph/218

#218 switch from SL4 to SL5