Fix exception message typo
Merge pull request #140 from twined/master

Fix exception message typo
Add support for case-insensitivity in MethodOverride

Now the `Plug.MethodOverride` plug supports case-insensitive methods both in the
`_method` parameter and in the `X-HTTP-Method-Override` header. I also updated
the docs for this plug.
Drop support for the X-HTTP-Method-Override header in Plug.MethodOverride

Now only the `_method` parameter is supported.
Merge pull request #141 from whatyouhide/method-override-for-custom-methods

Add support for custom methods in MethodOverride
Split error handling into its own module
Make debugger and error handler late bind