This changes allow to use parenthesis `(` `)` to encapsulate
expressions in addition to braces `{` `}` used to define blocks.
The main use-case is for arithmetic and boolean expressions for which
developers are used to using parenthesis. For example:
```
{ 14 + 42 } * 1337
```
can now be written as:
```
( 14 + 42 ) * 1337
```
This may sound straightforward at first but wasn't necessarily trivial
in Aiken given that (a) everything is an expression, (b) whitespaces
do not generally matter and (c) there's no symbol indicating the end
of a 'statement' (because there's no statement).
Thus, we have to properly disambiguate between:
```
let foo = bar(14 + 42)
```
and
```
let foo = bar
(14 + 42)
```
Before this commit, the latter would be interpreted as a function call
and would lead to a somewhat puzzling error. Now, the newline serves
as a delimiting symbol. The trade-off being that for a function call,
the left parenthesis has to be on the same line as the function name
identifier -- which is a fair trade off. So this is still allowed:
```
let foo = bar(
14 + 42
)
```
As there's very little ambiguity about it.
This fixes#236 and would seemingly allow us to get rid of the leading
`#` in front of tuples.
rvcas