Fix broken benchmarks

[lmb]

Re-creates the protobuf file from the text definition, and re-compresses both text and protobuf files.

Found this while working on #48. Without this change, text.gz is missing, protobuf.gz broken and the protobuf definition outdated.

PASS
BenchmarkParseText-4                    2000        886160 ns/op
BenchmarkParseTextGzip-4            --- FAIL: BenchmarkParseTextGzip-4
    bench_test.go:73: open testdata/text.gz: no such file or directory
BenchmarkParseProto-4               --- FAIL: BenchmarkParseProto-4
    bench_test.go:111: proto: can't skip unknown wire type 7 for io_prometheus_client.MetricFamily
BenchmarkParseProtoGzip-4           --- FAIL: BenchmarkParseProtoGzip-4
    bench_test.go:131: gzip: invalid header
BenchmarkParseProtoMap-4            --- FAIL: BenchmarkParseProtoMap-4
    bench_test.go:166: proto: can't skip unknown wire type 7 for io_prometheus_client.MetricFamily
BenchmarkDiscriminatorHTTPHeader-4    100000         19813 ns/op
BenchmarkCreate-4                      20000         65743 ns/op
BenchmarkCreateError-4                100000         12259 ns/op
BenchmarkTextParse-4                    5000        301804 ns/op
BenchmarkParseError-4                  30000         51406 ns/op
ok      github.com/prometheus/common/expfmt 11.032s

[beorn7]

Great. Thank you. And sorry for the wait.