Add parser and AST, remove some stuff from lexer

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

Cargo.lock

@@ -21,12 +21,6 @@ version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
-[[package]]
-name = "maplit"
-version = "1.0.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3e2e65a1a2e43cfcb47a895c4c8b10d1f4a61097f9f254f183aee60cad9c651d"
-
 [[package]]
 name = "memchr"
 version = "2.3.3"
@@ -38,7 +32,6 @@ name = "not-python"
 version = "0.1.0"
 dependencies = [
  "lazy_static",
- "maplit",
  "regex",
  "snafu",
 ]