v0.3: Asymptote 0.3

There were 17 commits since v0.2.0.
Of those 17, ten commits changed search and evaluation and two are only
speed optimizations. Those ten commits include the following changes (in
no particular order):
  * The Queen is valued more highly now (value of two rooks).
  * The amount of internal iterative deepening in zero window nodes is
    reduced.
  * Knight mobility now excludes squares attacked by enemy pawns.
  * Nullmove pruning is tried more often.
  * The maximum depth for late move reduction is increased.
  * Pawn mobility is considered.
  * Knight and bishops now each have a piece-square table.
  * Isolated pawns are penalized.
  * Captures of the last moved piece are searched deeper.
  * The weighting of knight, bishop and rook mobility has been tuned.

v0.2.0: Asymptote v0.2

There were 31 commits since v0.1.8. All but two were changes in the
engine, the remaining two were fixes for continuous integration builds.

Besides some slight optimization, fixes and code cleanups this release
includes the following changes (in no specific order):
  * a slightly tuned piece-square table for pawns
  * a piece-square table for rooks
  * a hash table of pawn evaluations
  * nullmove searches now are performed:
      * irrespective of depth
      * if the static evaluation is at least a pawn above alpha
      * with greater reduction
  * potential pricipal variations are searched to greater depth
  * futility pruning now has a depth-dependent cutoff value
  * move history scores are reset on each new search
  * use of an aspiration window of initially half a pawn above and below
    the current score

Additionally, the following non-UCI option was added:
  * ShowPVBoard: If set to true, Asymptote prints the board at the end
    of the current principal variation each time the principal variation
    is printed.

v0.1.8

Fix feature names for windows builds

v0.1.7

Fix windows build (hopefully)

v0.1.6

Use AppVeyor for Windows builds

v0.1.5

Fix Travis credentials