add support for generics in reflect mode

[MartinForReal]

Parse TypeParameters from type name only when "[]" is present in type name. related: #128

[CLAassistant]

All committers have signed the CLA.

[MartinForReal]

@r-hang PTAL. Thanks!

[bcho]

Does your implementation work for cases like

• foo.T[int[], bool, string[]]
• foo.T[bool[], context.Context[], github.com/foo/bar.X[], int[]]

[bcho]

also see: https://github.com/uber-go/mock/issues/97