Merge pull request #263 from rvandermeulen/explicit-compression-options

Mark the CompressionOptions(int) constructor explicit

snappy.h

diff --git a/snappy.h b/snappy.h
index 1c44868..11fb8ac 100644
--- a/snappy.h
+++ b/snappy.h
@@ -69,7 +69,7 @@
     int level = DefaultCompressionLevel();
 
       constexpr CompressionOptions() = default;
-      constexpr CompressionOptions(int compression_level)
+      constexpr explicit CompressionOptions(int compression_level)
           : level(compression_level) {}
 
     static constexpr int MinCompressionLevel() { return 1; }