Add support for 'Bearer token' style header

[ekryski]

It should also probably be the first priority. It's as simple as changing these lines to these:

jwtFromRequest: ExtractJwt.fromExtractors([
    ExtractJwt.fromAuthHeader()
    ExtractJwt.fromHeader(jwtSettings.header.toLowerCase()),
    ExtractJwt.fromBodyField(jwtSettings.bodyKey)
])

and writing a quick test.

[timelesshaze]

Fixed by #6

The method fromAuthHeader only checks headers in the form of "Authorization: JWT {token}".
Maybe this should be added anyway, but most implementations prefer Bearer.

This checks for Bearer in a case-sensitive manner, but that should be fine according to RFC6750.

[ekryski]

Fixed by #6