Enable filtering by numeric range

[eweitz]

This enables filtering Ideogram annotation values by a continuous numeric range. Such annotation values might include:

• log₂(fold change)
• p-value
• Gene expression (e.g. in TPM, RPKM, FPKM, or count)

Example filters for analyzing differential expression of genes, comparing space flight and ground control in NASA GeneLab data:

[coveralls]

Coverage decreased (-0.1%) to 90.806% when pulling 9593db8 on differential-expression into eb43ec7 on master.