2.6.2: Dynamic members fix

• Fixed issue with dynamic instance references not being emitted
  correctly, e.g. $value->{$field->get()};, see
  http://php.net/manual/en/functions.variable-functions.php
  (@thekid)

2.6.1: String parsing fix

• Fixed issue #41: String parsing of escapes broken - @thekid

2.6.0: Unicode escape sequences

• Implemented support unicode escape sequences in PHP 5.6, see #38
  (@thekid)
• Fixed issue #39: Syntax error for parameters called "function"
  (@thekid)
• Dropped confusing way of compiling multiple sources using -b to
  strip bases. New way is to pass multiple directories directly, e.g.
  $ xp compile -o dist src/main/php/ src/test/php
  (@thekid)
• Fixed compiling to a directory when the source path was not inside
  the current directory.
  (@thekid)

2.5.1: Line number fixes

• Ensured line number is always present for type members. Previously,
  this was 0, leading to output formatting errors
  (@thekid)
• Made some minor performance improvements by reusing nodes in two
  cases - return statements and assignments
  (@thekid)

2.5.0: Null-safe instance operator

• Implemented feature request #9: Support null-safe instance operator
  (@thekid)

2.4.0: Improved error messages

• Added context to various parse errors. Now messages read something
  like Expected ",", have "(end)"" in parameter list.
  (@thekid)
• Improved error messages: Include file name (w/o full path) and line
  number in exceptions raised from class loading.
  (@thekid)

2.3.0: Using

• Merged PR #33: Using statement - @thekid

2.2.0: Typed class constants

• Fixed typed properties inside comma-separated listing, for example:
  private string $a, int $b
  (@thekid)
• Implemented support for typed class constants const int T = 5
  (@thekid)

2.1.0: Compile to directory

• Implemented support for mixed type, see issue #28 - @thekid
• Fixed issue #32: Test suite failure on HHVM 3.25 - @thekid
• Allowed trailing commas in grouped use lists as implemented in
  https://wiki.php.net/rfc/list-syntax-trailing-commas
  (@thekid)
• Fixed nullable value types being emitted incorrectly - @thekid
• Merged PR #30: Implement compiling to directory. The command line
  xp compile src/main/php dist/ will compile all source files inside
  the src/main/php directory to dist.
  (@thekid)

2.0.5: Apidoc comments fix

• Fixed apidoc comments for methods, traits and interfaces - @thekid