Allow CORS on discovery endpoint

Bump go-oidc package

connector/ldap: enable groupSearch to be empty

*: add 'make revendor' and tests to catch incorrect glide usage

Introducing glide-vc caused us to unknowingly removed our Go
protobuf compiler (since it's a main). Add flags to glide-vc usage
to remedy this.

Since we now require several glide and glide-vc flags, add a Makfile
target and tests to catch when PRs don't use the correct flags.

build fails

replace bcrypt hash with a working one

replace bcrypt hash with an appropriate value for the string "password"

server: use UTC timestamps in dex.

storage: fix postgres timezone handling

server: add error HTML templates with error description.

Dex's Postgres client currently uses the `timestamp` datatype for
storing times. This lops of timezones with no conversion, causing
times to lose locality information.

We could convert all times to UTC before storing them, but this is
a backward incompatible change for upgrades, since the new version
of dex would still be reading times from the database with no
locality.

Because of this intrinsic issue that current Postgres users don't
save any timezone data, we chose to treat any existing installation
as corrupted and change the datatype used for times to `timestamptz`.
This is a breaking change, but it seems hard to offer an
alternative that's both correct and backward compatible.

Additionally, an internal flag has been added to SQL flavors,
`supportsTimezones`. This allows us to handle SQLite3, which doesn't
support timezones, while still storing timezones in other flavors.
Flavors that don't support timezones are explicitly converted to
UTC.

cmd/dex: provide better feedback when parsing config

cmd/dex: modify error messages to info messages.

*: fix comment typos and add go report card icon

*: check go version before building

cmd/dex: add logging config and launch logger for server module.

Add a script to check the Go version before building dex. This
gives a nice error message rather than just failing to compile.

With changes:

    $ go version
    go version go1.6.4 linux/amd64
    $ make
    ERROR: dex requires Go version 1.7+. Please update your Go installation: https://golang.org/dl/
    Makefile:93: recipe for target 'check-go-version' failed
    make: *** [check-go-version] Error 2

Checks only added for building the actual binary, not tests, since
this is aimed at users just starting off with the project.