...before calculating the head table checksum. Per the head table specification:

> checkSumAdjustment: To compute set it to 0, calculate the checksum for the 'head' table and put it in the table directory, sum the entire font as a uint32_t, then store 0xB1B0AFBA - sum. (The checksum for the 'head' table will be wrong as a result. That is OK; do not reset it.)

ref #123

The number of tables in the font may change when generating a font file. Because the font header is dependent on the number of tables the values need to be recalculated.

ref #123

Per the spec:

> Table checksums are the unsigned sum of the longs in a table.

Per the spec:

> The length of any table is a multiple of four bytes, or that tables are padded with zero to four byte-aligned offsets. Actual table lengths recorded in the TableDirectory should not include padding.

fixes #119

Before this change when the font loca table was using the short format (glyph size / 2), an odd-numbered glyph byte length would be incorrectly record. To prevent this issue, when writing a font we will padd glyphs to align with a 4-byte boundary.

Note: Official guidance needed. The 4-byte boundary is based on table requirements, as well as being a multiple of 2.

Most name strings should be encoded with UTF-16BE per the spec, but there are situations where other encodings are required or acceptable. This change only addresses a subset of potential encodings.

fixes #70

A font with a format 2 cmap table will still re-encode with a format 4 cmap table.

relates to #123

This librarry relies on Unicode data for a number of functions (namely font re-encoding). Without a Unicode-encoded cmap table those functions do not work as expected.