organize top level files

Remove .gitattributes, we don't have any of these files now.
Move fuzzit.sh -> tools/fuzzit.sh.

.gitattributes

@@ -1,3 +0,0 @@
-executor/defs.h     linguist-generated
-executor/syscalls.h linguist-generated
-sys/*/gen/*.go      linguist-generated

.travis.yml

@@ -40,7 +40,7 @@ jobs:
       if: branch = master AND type IN (pull_request)
       go: 1.14
       script:
-        - ./fuzzit.sh local-regression
+        - tools/fuzzit.sh local-regression
 
     - stage: fuzzit.dev (fuzzing)
       if: branch = master AND type IN (push)
@@ -48,4 +48,4 @@ jobs:
       env:
         secure: "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"
       script:
-        - ./fuzzit.sh fuzzing
+        - tools/fuzzit.sh fuzzing