ENH: Basic checks on data

[dgursoy]

Proposed functions for checking content:

contains_nans: Check if data contains NaN elements.
contains_negs: Check if data contains negative elements.
contains_zeros: Check if data contains zeros.
contains_outliers: Check if data has outlier values.

Proposed functions for checking data types:

is_ndarray: Check if an array is a Numpy array.
is_numeric: Check if data is numeric.
is_bool: Check if data is bool.
is_int: Check if data is integer.
is_float: Check if data is float.
is_complex: Check if data is complex.

Proposed functions for checking data shape:

is_square: Check if a 2D array dimensions are the same.
is_shape: Check if a array dimensions are the same as provided shape.