CLI: rename --file to --assemblefile

[jonschlinkert]

I think we should be more specific with flags, especially since we're planning to add support for project-generators soon. In project generators, users might use minimist directly with flags like --file to specify templates or whatever.

I just wanted to post this before we deprecate in case anyone has any pushback, feedback or alternatives.

[assemblebot]

@jonschlinkert Thanks for the issue! If you're reporting a bug, please be sure to include:

• The version of assemble you are using.
• Your assemblefile.js (This can be in a gist)
• The commandline output. (Screenshot or gist is fine)
• What you expected to happen instead.

If your issue is related to one of the following, please open an issue there:

• grunt-assemble Issues with using assemble in grunt or the grunt-assemble library.
• handlebars-helpers Issues with using handlebars helpers from the handlebars-helpers library.