use circleci instead of travis (#511)

Upgrade rust-toolchain
Upgrade Tantivy
Warning: tantivy now use a different file format, search index may need to be deleted and recreated to work as intended
try to run compile twice in a row because sometime oomk is evil

script/compute_coverage.sh

@@ -1,12 +1,5 @@
-#!/bin/bash
-wget https://github.com/SimonKagstrom/kcov/archive/master.tar.gz &&
-tar xzf master.tar.gz &&
-mkdir -p kcov-master/build &&
-cd kcov-master/build &&
-cmake .. &&
-make &&
-sudo make install &&
-cd ../.. &&
+#!/bin/bash 
+set -eo pipefail
 for file in target/debug/*-*[^\.d]; do
 	if [[ -x "$file" ]]
 	then
@@ -14,6 +7,5 @@ for file in target/debug/*-*[^\.d]; do
 		mkdir -p "target/cov/$filename"
 		kcov --exclude-pattern=/.cargo,/usr/lib --verify "target/cov/$filename" "$file"
 	fi
-done &&
-bash <(curl -s https://codecov.io/bash) &&
-echo "Uploaded code coverage"
+done
+bash <(curl -s https://codecov.io/bash)