Update readme.txt

Spelling mistake.
-Upgraded to Immutable Collections RTM
-Added missing CLSCompliant attributes
Merge pull request #106 from RenniePet/master

Update readme.txt
-Fixed not parsing some ISO date timezones
-Fixed float schema validation of integer values
-Changed writing of IConvertible values to convert objects to strings
-Fixed serializing proxy objects with no default constructor
Merge branch 'master' of github.com:JamesNK/Newtonsoft.Json
-Added support for serializing extension data
-Added support for reference loop handling and type name handling to extension data
-Bug fixes
-Added XML documentation
-Fixed various compiler warnings
-Tests
-Increment version to 5.0.7
-Added default value and required support to constructor deserialization
-Fixed build warning
-Fixed documentation IE7 JS error
-Fixed build warnings
-Fixed build warnings
-Build
-Fixed WinRT build
-Remove accidental files
-Documentation
-Fixed WinRT
-Changed license URL
-Fixed not quoting strings when QuoteName is false
-Increment version to 5.0.8