Fix dashes in Haskell module names

[unclechu]

This fixes dashes appearing in generated Haskell module names when youhave *.proto files which have dashes in their names. For instance if you name your *.proto file like this: foo-bar-baz.proto you get Foo-bar-baz Haskell module name which is just broken.

With this fix if I name proto file like foo-bar---baz.proto I get module FooBarBaz where in the FooBarBaz.hs Haskell file.

Test example:

$ printf 'syntax = "proto3";\npackage foo;\n' > foo-bar---baz.proto
$ compile-proto-file --proto foo-bar---baz.proto --out x
$ grep '^module' x/FooBarBaz.hs
module FooBarBaz where