Recover broken find pattern for UNIX

ref: codecov#184

Removing brackets from find arguments (a4cc565) has affected to the
result of finding coverage files. This commit reverts brackets to get
back the original search condition.

Previously brackets were escaped by backslash to avoid opening sub-shell
on the shell environment, but no longer need backslashes because of
using `execFileSync()` that is disabled shell environment by default.

lib/codecov.js

@@ -20,7 +20,8 @@ var isWindows =
 
 if (!isWindows) {
   patterns = (
-    "-type f -name '*coverage.*' " +
+    '-type f ( ' +
+    "-name '*coverage.*' " +
     "-or -name 'nosetests.xml' " +
     "-or -name 'jacoco*.xml' " +
     "-or -name 'clover.xml' " +
@@ -32,6 +33,7 @@ if (!isWindows) {
     "-or -name 'gcov.info' " +
     "-or -name '*.gcov' " +
     "-or -name '*.lst' " +
+    ') ' +
     "-not -name '*.sh' " +
     "-not -name '*.data' " +
     "-not -name '*.py' " +