Generate text data type as textarea

[acangiano]

Currently, mix phx.gen.html (and mix phx.gen.live) generate a single-line input field even if the user specifies text as the data type. For example:

mix phx.gen.html Blog Post posts title:string body:text

will generate the following form which is not what most users would expect.

In essence, there is no distinction between string and text types as far as the generated HTML goes (though, the distinction exists in the generated migration file).

This small patch allows for fields declared as text to be generated as <textarea>.