Move query to its own subpackage (#152)

Move all the query system to its own package. The reason is to
avoid it to rely on unexported methods and structures, and move
it out of the main package since this is really not a core
feature. It is still tied to the toml.TomlTree and toml.Position
structures for now.

* Move query mechanism to its own subpackage
* Rename QueryResult to Result to avoid stutter
* Add query.CompileAndExecute

Fixes #116

test.sh

@@ -19,6 +19,9 @@ function git_clone() {
   popd
 }
 
+# Remove potential previous runs
+rm -rf src test_program_bin toml-test
+
 # Run go vet
 go vet ./...
 
@@ -36,13 +39,16 @@ go build -o toml-test github.com/BurntSushi/toml-test
 # vendorize the current lib for testing
 # NOTE: this basically mocks an install without having to go back out to github for code
 mkdir -p src/github.com/pelletier/go-toml/cmd
+mkdir -p src/github.com/pelletier/go-toml/query
 cp *.go *.toml src/github.com/pelletier/go-toml
 cp -R cmd/* src/github.com/pelletier/go-toml/cmd
+cp -R query/* src/github.com/pelletier/go-toml/query
 go build -o test_program_bin src/github.com/pelletier/go-toml/cmd/test_program.go
 
 # Run basic unit tests
-go test github.com/pelletier/go-toml -v -covermode=count -coverprofile=coverage.out
+go test github.com/pelletier/go-toml -covermode=count -coverprofile=coverage.out
 go test github.com/pelletier/go-toml/cmd/tomljson
+go test github.com/pelletier/go-toml/query
 
 # run the entire BurntSushi test suite
 if [[ $# -eq 0 ]] ; then