Changes since Idris 2 v0.1.0

Compiler updates:

Data types with a single constructor, with a single unerased arguments, are translated to just that argument, to save repeated packing and unpacking. (c.f. newtype in Haskell)
0-multiplicity constructor arguments are now properly erased, not just given a placeholder null value.

Other improvements:

Various performance improvements in the typechecker:
- Noting which metavariables are blocking unification constraints, so that they only get retried if those metavariables make progress.
- Evaluating fromInteger at compile time.
- In the run-time, reuse the old heap after garbage collection if it hasn't been resized, to avoid unnecessary system calls.
Extend Idris2's literate mode to support reading Markdown and OrgMode files. For more details see: https://idris2.readthedocs.io/en/latest/reference/literate.html
Fields of records can be accessed (and updated) using the dot syntax, such as r.field1.field2 or record { field1.field2 = 42 }. For details, see https://idris2.readthedocs.io/en/latest/reference/records.html

Changes since Idris 1