incorrect type for the --cost-per-month and --setup-fee options

[nmasse-itix]

Current behavior

$ 3scale application-plan apply nmasse-redhat beer_catalog_0 test --cost-per-month=3.14
apply: invalid value "3.14" for --cost-per-month option

$ 3scale application-plan apply nmasse-redhat beer_catalog_0 test --setup-fee=3.14
apply: invalid value "3.14" for --setup-fee option

Expected behavior

Costs / fees in application plans are not restricted to integers but can accept cents in addition to dollars/euros (which is possible by editing manually the application plan in the admin portal).

$ 3scale application-plan apply nmasse-redhat beer_catalog_0 test --cost-per-month=3.14
Applied application plan id: 2357356088490; Default: false

$ 3scale application-plan apply nmasse-redhat beer_catalog_0 test --setup-fee=3.14
Applied application plan id: 2357356088490; Default: false