Merge pull request #12 from ptgreen/master

Misc work on LALR parser.
Add a new test script to evaluate status of different parsers.
Add keywords to unpaired_token rule.
Add low-precedence lambda variant of '|'.
Fix bug in exprs.
Add expr_nostruct to handle restriction on 'expr' in 'while expr { ... }'
Permit empty match clauses.
Fix '_' rules in pat and ty.
Separate out block and permit no-comma block match arms.
Add ExprVec.
Add rule to lexer for STATIC.
Add machinery for decaying >> to > > in end of type-arg/param lists.
Flesh out rules for structs.
Permit following a block match arm with a nonblock match arm.
Fix for loop to take pat, not expr in head position.
Support explicit self in method and type_method.