[libfuzzer] update Efficient Fuzzer Guide and small fixes to documentation.

testing/libfuzzer/getting_started.md

 # Getting Started with libFuzzer in Chrome
 
 *** note
-**Prerequisites:** libFuzzer in chrome is supported with GN on Linux only. 
+**Prerequisites:** libFuzzer in Chrome is supported with GN on Linux only. 
 ***
 
 This document will walk you through:
 
 * setting up your build enviroment.
 * creating your first fuzzer.
 * running the fuzzer and verifying its vitals.
 
 ## Check Out ToT Clang
 
@@ skipping 48 matching lines @@
   deps = [ ... ]
 }
 ```
 
 ## Build and Run Fuzzer Locally
 
 Build with ninja as usual and run:
 
 ```bash
 ninja -C out/libfuzzer url_parse_fuzzer
-./out/libfuzzer url_parse_fuzzer
+./out/libfuzzer/url_parse_fuzzer
 ```
 
 Your fuzzer should produce output like this:
 
 ```
 INFO: Seed: 1787335005
 INFO: -max_len is not provided, using 64
 INFO: PreferSmall: 1
 #0      READ   units: 1 exec/s: 0
 #1      INITED cov: 2361 bits: 95 indir: 29 units: 1 exec/s: 0
@@ skipping 27 matching lines @@
 * Check the [Efficient Fuzzer Guide] to better understand your fuzzer
 performance and for optimization hints.
 
 
 [Address Sanitizer]: http://clang.llvm.org/docs/AddressSanitizer.html
 [Memory Sanitizer]: http://clang.llvm.org/docs/MemorySanitizer.html
 [url_parse_fuzzer.cc]: https://code.google.com/p/chromium/codesearch#chromium/src/testing/libfuzzer/fuzzers/url_parse_fuzzer.cc
 [ClusterFuzz status]: clusterfuzz.md#Status-Links
 [Efficient Fuzzer Guide]: efficient_fuzzer.md
 [crbug/598448]: https://bugs.chromium.org/p/chromium/issues/detail?id=598448