Create a standalone pdfium build.

I moved pdfium_test from chromium's repo to pdfium's. It's now buildable as a sample following the instructions on the wiki.
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..06184bd
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,18 @@
+/build/Debug
+/build/Release
+/build/gyp
+/out
+/v8
+/xcodebuild
+Makefile
+.DS_Store
+*.filters
+*.mk
+*.opensdf
+*.pyc
+*.sdf
+*.sln
+*.suo
+*.user
+*.vcxproj
+*.xcodeproj
\ No newline at end of file