Fixes to CSV download and internal code cleanup

Changes since v1.4 Release

• 'all' column default sorts again
• Minor style fixes for gradients and colors
• Fixed CSV download having incorrect headers
• Added hsa-miRNA_count' to cvs download
• Code cleanup to decouple displayed column data
• Added links for adding github bug reports and feature requests.

Added H4 and GL261 cells

• Added data for human "H4" brain cell
• Added data for mouse "GL261" brain cell
• Enlarged autocomplete window max-size
• Viability gradient now includes orange midpoint
• mirBase links now open new tab
• Formatting adjustments

Added autocomplete to miRNA search field

• Added EasyAutocomplete jQuery library.
• Added autocompletion dropdown list for miRNA search field.
  • Color-codes for each miRNA are displayed to their left.
  • Selecting an entry (clicking or arrows+enter) performs a search for its corresponding Seed.
• Added 'How to Use' section with screenshots.
• Added '?' button in header to jump to 'How to Use' section.
• Simplified 'Info' section
• Modified mature miRNA button styles
  • Purple outlines are now consistent
  • Added hover colors for Drosha and miRtrons
  • Outline now has consistent width on all sides

Added info on miRtrons

• miRNA data modified to include is_mirtron boolean field.
• miRtrons now have blue outlines.
• Thickened miRNA outline boxes.
• Updated Info section and Version History text.

Added info on Drosha processed miRNAs

• miRNA data modified to include is_drosha_processed boolean field.
• miRNA preview in table now uses a yellow box if miRNA is drosha processed.
• Added drosha details for miRNAs to Info section.

Added Version History

• Version history section in footer
• Version history is dynamically pulled from github releases.
• Latest release version appears in page title