Better error message for no method

A simple PR to improve the error message shown when calling a function without a particular method. Resolves issue noted in: https://github.com/JuliaLang/julia/issues/7396

As an example:
```julia
less(0)
Error: no method less(Int64)
```

Will be replaced with a more descriptive error message:
```julia
less(0)
ERROR: function less has no method with signature (Int64)
```

I also fixed some whitespace issues where function arguments weren't separated by a space.