Allow imports from self-signed SSL hosts

When working on some development environments, it may be useful to import less files from a remote host that uses a self-signed certificate. When using less 1.3.x and less, it was working without any issues, but since 1.4.x it is not possible anymore and fail silently.

This pull request adds a switch named ```--insecure``` to the binary that allows circumventing the default check made by ***request*** for those specific cases, as well as an ```insecure``` option provided to the parser.