more testing to be defensive against slightly odd behavior in underlying s-exp lib
bootstrapped with s-exp updates
Merge branch 'master' of github.com:brownplt/pyret-lang
type instantiation now parses correctly. Here's why:
 - All symbolic operators require whitespace on both sides
   (+ - * / >= <= > < <> ==
    - Should "and" "or" "raises" and "satisfies" require that too?
 - type instantiation and friends no longer accept LT and GT
Operators now all require whitespace on either side
All operators now parenIsForExp: true
newlines before and after operators
Factor out common bits of operator regexes with helper function
Caret is now an op, put with the other ops (moved over disjoint regexps)
Match trailing whitespace with more tokens (see table below)

              | check + match  | have
              | trailing space | `parenIsForExp` set
--------------+----------------+--------------------
`COMMA`       |                |        X
`THINARROW`   |                |
`THICKARROW`  |       X        |        X
`COLONCOLON`  |       X        |
`COLON`       |                |        X
`EQUALS`      |                |        X
`COLONEQUALS` |                |        X
Adding space around caret / cannonball operator in both src and tests
Update Bootstrap grammer
Update Bootstrap tokenizer