Merge pull request jupp0r#273 from jupp0r/propagate-curl-errors Fix push gateway code

Revert "Do a verbose build on travis" This reverts commit e243c7b.

Merge pull request jupp0r#158 from jupp0r/update-google-test-to-1.8.1 Update googletest submodule to 1.8.1

Merge pull request jupp0r#132 from jupp0r/gcc48-compatibility GCC 4.8 compatibility

Merge pull request jupp0r#108 from jupp0r/bugfix/fix-compile-error-wi… …th-gcc-7 Fix GCC 7 compile error

Merge pull request jupp0r#105 from jupp0r/replace-protobuf Remove protobuf dependency This change removes the protobuf wire format, as it's no longer supported in prometheus 2.0. It uses this as an opportunity to remove protobuf as an external dependency all together, which will make integration into existing code bases that already use protobuf much more palatable.

Merge pull request jupp0r#93 from jupp0r/feature/remove-json-output Remove JSON Serializer

Merge pull request jupp0r#80 from khabinov/khabinov/fix-histogram-bou… …ndaries Histogram boundary value should be inclusive

Merge pull request jupp0r#64 from jupp0r/feature/fix-benchmark-counte… …r-naming Fix benchmark metrics naming

Merge pull request jupp0r#63 from jupp0r/feature/reduce-scraping-threads Reduce number of threads for scrape server